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Imagecat This article is about the battle. For the initial quantum event, see Resonance Cascade.
Imagecat For other uses, see Black Mesa (disambiguation).

"Prepare for unforeseen consequences."
The G-Man[src]

The Black Mesa Incident, also referred to as the Lambda Incident,[17] was a catastrophic event resulting from an experiment carried out by the Anomalous Materials department at the Black Mesa Research Facility. The insertion of an especially pure Xen crystal into the Anti-Mass Spectrometer triggered a rare quantum event known as a Resonance Cascade, which ruptured the space-time continuum and allowed extradimensional beings from a realm known as the Borderworld to teleport into the facility.

Black Mesa personnel who had survived the initial incident attempted a resonance reversal using an orbiting satellite to seal the tear. The attempt failed and it was deduced that a powerful being was deliberately holding the rift open. The survivors quickly realized the presence of the aliens was not an accident, and were in fact the vanguard of an invasion.

The United States government dispatched a military expeditionary force to the facility to contain the invasion and silence witnesses, however, they suffered heavy casualties and were compelled to quickly withdraw. The ensuing desperate conflict between the survivors and increasing numbers of alien creatures led to the government authorizing the facility's destruction with a nuclear device, which destroyed the facility and eradicated the invasion.

Prior to the facility's destruction, Black Mesa scientist Gordon Freeman had been teleported to the Borderworld by the Lambda Team, where he successfully killed the creature coordinating the invasion and holding the rift open. Freeman's whereabouts would remain unknown for decades, as he disappeared immediately after these events.

Though Freeman's actions halted the invasion, the portal storms that occurred as a consequence of the incident continued to intensify, ultimately attracting the attention of a powerful interdimensional empire known as the Combine to launch an invasion and subsequent occupation of Earth in only 7 hours.


Sometime prior to the Incident, researchers at the Black Mesa Research Facility had discovered an extradimensional realm, formally known as the Borderworld, but colloquially referred to as Xen, while developing teleportation technology.[18] Attracted by scientific curiosity, particularly toward the properties of exotic minerals found on the alien world to aid in their teleportation research, Black Mesa's Lambda Team launched multiple survey expeditions to the Borderworld to collect samples of Xenian flora and fauna.[18] The Xenian biosphere was incredibly hostile, and thus these expeditions were considered extremely hazardous, resulting in the death or capture of dozens of researchers. Despite this, many samples of Xenian animal and plant life were retrieved for study in the Sector E Biodome Complex,[19][20] while the exotic minerals were studied in the Sector C Test Labs.[21]

Ba xen50001

Research equipment set up by the survey teams on Xen

Aside from key personnel in the Lambda Team, many of Black Mesa's scientists were not appraised of the true source of the Xenian samples that were retrieved; for example, scientists studying an Ichthyosaur were told that the creature originated from Challenger Deep in the Pacific Ocean,[22] while scientists studying the mineral samples often speculated with one another about their origin.[23]

Under the design supervision of Dr. Rosenberg,[24] Black Mesa personnel constructed an Anti-Mass Spectrometer in Test Lab C-33/a to study the retrieved mineral samples, with the research team itself led by Dr. Eli Vance, Dr. Richard Keller, and Dr. Isaac Kleiner. On May 11, research associate Dr. Colette Green received a memo indicating that the supervision team were particularly interested in newly-acquired mineral sample GG-3883. Green's own analysis on the sample revealed unexpected spectral fluctuations, however it was identified as the largest and purest sample the team were able to retrieve. In violation of standard anomalous materials handling protocol, the supervision team ordered that the new sample replace the original chosen sample EP-0021 in the experiment.[25]

On the day of the experiment, in a deviation from standard analysis procedure, the Sector C research team were ordered to over-clock the Anti-Mass Spectrometer and run its power resolution at 105%, much higher than the scanner's safety buffer zone of under 90%. While some personnel expressed consternation at the breach of protocol, others supported the move since the extra resolution would allow them to garner more data.[26][27] Two of the lead researchers, Dr. Eli Vance and Dr. Rosenberg both vehemently protested the decision, but were overruled.[28][29]

These instructions came directly from the office of the Black Mesa Administrator, Wallace Breen, who was allegedly keen to gain conclusive results from the experiment. However, some personnel suspected the interference of another individual in matters, who, according to Dr. Vance, had also personally delivered the new sample GG-3883 to the labs.[28][30]

With the concerns of the researchers overruled, the Anti-Mass Spectrometer was prepared at the new power level of 105%.[27] Because of the immense power output required, Black Mesa experienced several minor brownouts across the facility.[31] The experiment was initially delayed due to Dr. Gordon Freeman, the manual operator of the Anti-Mass Spectrometer, having overslept.[32] However, this delay was actually convenient for the research team, who used the time to undertake further preparations and to also recover from a facility-wide system crash which resulted in a minor data loss.[30]

Dy accident10009

Dr. Cross and Dr. Green oversee the Anti-Mass Spectrometer

Following Dr. Freeman's arrival, research associate Dr. Gina Cross delivered the mineral sample to the test chamber, while Dr. Cross' colleague, Dr. Green operated the Anti-Mass Spectrometer from its lower maintenance level.[27] Lead researcher Dr. Eli Vance was contacted by an unknown third-party, who whispered to him to "prepare for unforeseen consequences". Dr. Vance briefly contemplated aborting the experiment, but ultimately decided against it.[28] Freeman activated the Anti-Mass Spectrometer without incident, and the supervising researchers increased its power level to 105%, as stipulated. One of the researchers monitoring from the control room noticed a small discrepancy in the readings, but dismissed his concerns as it remained within acceptable parameters.[33]

The mineral sample arrived in the test chamber, and Freeman inserted the delivery cart into the Anti-Mass Spectrometer's plasma stream. The immediate result was catastrophic: the plasma stream agitated the exotic matter contained within the sample, and triggered an overload in the equipment, causing several minor explosions. The monitoring team attempted to shut down the device but to no avail, before a stray beam of plasma destroyed the control room, killing the researchers. As the equipment continued to go critical, a Resonance Cascade occurred, tearing a rift in the space-time continuum, forcibly drawing extradimensional creatures into the facility.[30]

Immediate effects and military response[]

The Resonance Cascade inflicted severe structural damage to the facility, particularly in the immediate radius of the Anti-Mass Spectrometer, while a local electromagnetic pulse disabled all external communications.[34][31] The Xenian creatures, trapped in an alien environment, reacted with fear and hostility by attacking surviving Black Mesa personnel on site.


The Resonance Cascade

Dr. Gordon Freeman, who survived thanks to the HEV Suit, managed to locate Dr. Eli Vance, who instructed Freeman to proceed to the surface to call for help.[34] Survivors Dr. Gina Cross, Dr. Colette Green, and Dr. Rosenberg, under the direction of Dr. Richard Keller, managed to reach the surface where they successfully transmitted a distress call to request military support in containing the alien lifeforms.[35] The United States government quickly dispatched the Hazardous Environment Combat Unit, deploying troops, ordnance, and establishing checkpoints to contain the creatures. The troops overrode the Black Mesa Announcement System, placing it under military command. Aside from containing the aliens, the military were also instructed to silence surviving witnesses to the experiment.[36]

The military response was initially highly successful, quickly taking control of the facility, establishing fortified outposts and checkpoints, and dispatching platoons deeper into the facility to contain the alien incursion.[36] Troops also successfully captured Dr. Rosenberg, designer of the Anti-Mass Spectrometer who had transmitted the distress call, sealing him in a railway car for interrogation.[37] Though, not all was successful as some aircrafts were shot down by alien aircrafts.[38] One of these aircrafts shot down had Corporal Adrian Shepard. Barney Calhoun, a low-ranking security officer, recovered from a bout of unconsciousness following the Resonance Cascade and successfully freed Dr. Rosenberg. Rosenberg aimed to use the old teleporters in the abandoned A-17 Prototype Test Labs to escape from the facility.[39][40]

HL BMRF OfficeComplex

A dead scientist in the Sector D Office Complex.

Meanwhile, Dr. Freeman managed to reach the Sector D High Security Storage Facility, where he learned of the military's true mission to silence the facility personnel. Reaching the surface, Freeman discovered that airstrikes were in progress, compelling him to retreat back inside.[36][41]

Under the instruction of Dr. Keller, Dr. Green and Dr. Cross attempted to reactivate the Anti-Mass Spectrometer's damping locks to seal the rift, however their attempt was ineffective, leading Dr. Keller to speculate that an alien force was holding the rift open.[42] In collaboration with Dr. Keller, the Lambda Team concocted a plan to launch a satellite into orbit, which, when used in conjunction with a prototype displacement beacon, would help seal the rift. With a military air-traffic lockdown preventing the launch, Dr. Cross and Dr. Green successfully overrode the lockdown and allowed the rocket to be launched. However, the launch was aborted when military personnel captured the control room at the High Altitude Launch Centre and killed all its personnel.[43]

BMRF helipad Osprey

A V-22 Osprey deploying HECU troops into Black Mesa.


Power Up Garg

HECU soldiers battle a Gargantua near the monorail track turntable.

Forced back into the facility, Dr. Freeman was appraised of the Lambda Team's plan to seal the rift, and they requested his aid in resuming the satellite launch.[36] With the Black Mesa Transit System disabled, Freeman was forced to proceed across the facility on foot. Entering the Silo D Propulsion Test Labs, Freeman's progress was halted by a large Tentacle which had nested in the silo. Freeman activated the necessary fuel and power lines and fired the rocket, killing the Tentacle.[44] By this time, the HECU had identified Freeman as the scientist indirectly responsible for the Resonance Cascade, and marked him a priority target. Using the tracking devices in his HEV Suit, the troops set multiple ambushes along his route.[45][46]

Intending to ride an old still-functional monorail network from Sector E Materials Transport to the High Altitude Launch Centre, Freeman made his way deeper into the facility, where he found HECU forces clashing with a Gargantua, which easily dispatched the troops. Freeman lured the beast between two electrical generators and activated them, delivering a fatal shock which killed the creature, allowing him to proceed on.[47] Despite the HECU's frequent ambushes, Dr. Freeman reached the Launch Centre where he launched the rocket prepared by Dr. Green, Dr. Cross, and Dr. Keller.[46] Following the rocket's successful launch, Dr. Cross and Dr. Green manually raised and activated the displacement beacon, allowing Dr. Keller to initiate a resonance reversal. While the reversal lessened the effects of the interdimensional rift, it did not seal it completely, due to the interference of a powerful alien force from the other side.[48]

Rosenberg is pleased

Dr. Rosenberg overseeing the A-17 Teleporter

Unable to neutralize Dr. Freeman and suffering heavy casualties, it became clear that the HECU's attempted clean-up operation was failing. In response, the US government deployed a black operations unit to Black Mesa, with orders to destroy the facility with a thermonuclear device and silence all witnesses, human or otherwise.[49] Shortly after the arrival of the black operations team, two Vortigaunts, designated R-4913 and X-8973 successfully retrieved several stolen exotic minerals for their leader.[50] Meanwhile, Barney Calhoun managed to escape the facility after aiding Dr. Rosenberg in successfully establishing the Xenian teleport relay; using the old teleporters in the A-17 Labs, they escaped the facility in an SUV with their colleagues, Dr. Walter Bennett, and Dr. Simmons.[51]

Dy fubar0010

The displacement beacon initiating a resonance reversal

As Dr. Freeman attempted to make his way over to the Lambda Complex, he was ambushed and knocked unconscious by two HECU troopers. However, instead of taking him to the surface for interrogation as ordered, the two soldiers instead stripped him of his weapons and dumped his body into a trash compactor, intending to lie to their superiors that Freeman had been killed.[52] However, Freeman, who regained consciousness just in time, escaped the compactor and evaded the HECU by proceeding through the Biological Waste Processing Plant,[53] and negotiated his way through to the Advanced Biological Research Lab. There, Freeman discovered that many Xenian creatures were being forcibly contained and subjected to invasive experimentation and study, long before the Incident had even occurred.[54] Dislodging the military presence in the lab, Freeman began his journey across the surface.[55]

Meanwhile, the Xenian invaders had breached the surface in large numbers, turning the Black Mesa desert into a warzone. Xenian forces made use of extremely manoeuvrable organic aircraft to contest air superiority of the region; these aircraft shot down large numbers of V-22 Ospreys conveying HECU reinforcements to the facility.[38] Despite the heavy fire support rendered by M1A1 Abrams tanks, M2A3 Bradley IFVs, and AH-64 Apache gunships, the HECU forces suffered heavy casualties in personnel and materiel, compelling them to abandon their mission and initiate a retreat from Black Mesa.[55] Using the chaos to his advantage, Freeman successfully fought his way through the warring belligerents and reached the Lambda Complex.[55][56]

Hecu tank

HECU troops battling on the surface

Military withdrawal[]

Welcome to Black Mesa2

The wreckage of Cpl. Shephard's crashed Osprey

Corporal Adrian Shephard, one of the few survivors of his team, had awoken in the Black Mesa Medical Lab. Shepard makes his way through the facility and he stumbles upon the Black Mesa Transit System. After getting off the tram, he encounters a strange alien unlike the ones seen before in the facility. Adrian Shepard finally finds the HECU at the nearest extraction point, where he was informed of the HECU withdrawal.[57] However, the evacuation was woefully incomplete, leaving behind many troops, including Cpl. Shephard, and much of their equipment[58] Shephard has to go back into the facility after being abandoned.[59] To cover their retreat, the HECU authorized repeated airstrikes from F-16 warplanes, inflicting heavy damage on the facility.[60]

Meanwhile, Cpl. Shephard encountered several troops from his company who agreed to abandon their mission to neutralize Dr. Freeman and silence the remaining Black Mesa personnel, agreeing instead to search for an alternative escape route in collaboration with the surviving science team personnel.

Shepard makes his way through the facility and reaches the surface once more[49] and sees a door towards the Lambda Complex but it is locked. A medic is beside it who asks for an engineer. Cpl. Shephard finds a vent and sees Black Operation units. He finds out that they are not friendly towards the H.E.C.U. and so Shepard kills the units. He finds an engineer that needs medical help and opens another locked door to go back outside to lead the medic to the engineer. Shepard goes deeper into the facility and finds more Black Ops. He, along with two other Marines, kills more Black Ops and they get closer to the Lambda Complex.

While the majority of the Black Mesa survivors had congregated in the Lambda Complex, much of the facility had been overrun by the hostile creatures. Dr. Freeman accessed the reactor core and successfully reached the team of scientists waiting for him at the tip of the reactor.[18] A handful of surviving personnel, who had established a fortified position in one of the staging areas for the Borderworld survey teams, had long since deduced that the resonance reversal had been unsuccessful due to the influence of a powerful alien force on the other side, and concluded the being had to be killed for the rift to be sealed and the invasion halted. Agreeing to the plan, the team used the Lambda Complex's massive teleportation device to send Dr. Freeman to Xen.[18]

We Are Not Alone 3

Dr. Freeman enters the Borderworld

Mere seconds after Freeman's teleportation, an alien attack in the teleportation chamber severely damaged the teleporter. Cpl. Shephard, who had arrived in the chamber just prior to Freeman's departure, fought off the alien attack. Shepard saw this, and instead of going into the portal Dr. Freeman had just gone through, he decided to go travel to a different portal on the other side of the teleportation room which transported him to an area of Xen.[61] The Corporal, with help from the Borderworld's low gravity and bounce pads, jumped on some platforms floating in the dimension until he got to another higher portal teleporting Shephard back into Black Mesa.[20]

Final hours[]

While the situation at Black Mesa continued to deteriorate, a new and hitherto unknown foe appeared through the interdimensional tear, known only as "Race X".[62] This new foe began to attack everything in the facility, including Xenian creatures, in order to clear a path for a terraforming creature, hoping to colonize Earth.[63] After reaching Waste Processing Area 3, Cpl. Shephard and a contingent of HECU troops encountered and engaged a large Pit Worm. Shephard killed the creature by dumping toxic waste into its lair, and then proceeded to the surface.[62][64] Upon reaching the surface, the remnants of the HECU, black operations teams, surviving Black Mesa personnel, and the two alien invaders were engaged in a vicious five-way battle for supremacy.[65]

Black ops apache voltigore

Black operations troops engage alien creatures on the surface

Forced back underground by the fierce fighting, Cpl. Shephard discovered the US government's solution for the Incident: the black operations teams that had been deployed had armed a thermonuclear bomb in the Ordinance Storage Facility, intending to destroy the facility and wipe out the invaders. Shephard deactivated the device, but witnessed a mysterious individual reactivating it; with his path blocked, the fate of Black Mesa had been sealed.[66] Proceeding further, Shephard found that surviving Black Mesa and remaining HECU personnel were collaborating to prevent a large alien creature from settling and terraforming Earth for its own species. While the creature had killed the team sent to contain it, Shephard managed to blind and kill it, halting its invasion of Earth.[63]

Shortly thereafter, the thermonuclear device detonated, destroying Black Mesa and much of the surrounding area, ending the conflict.[67]

Shephard had awoken in a V-22 Osprey following his victory, far from the facility, confronted by a mysterious individual, seemingly affiliated with the government. The individual informed Shephard that he was a dangerous witness to events at Black Mesa, and while a directive had impelled the individual to dispatch of Shephard, he had instead chosen to indefinitely detain him after admitting an admiration for Shephard's survival ability.[2]


Xen islands 1

Gordon Freeman's first view of Xen.

Freeman arrives at Xen after his teleportation at the Lambda Complex, and is almost immediately contacted telepathically by the Nihilanth, the creature holding the portal open, who responds to Freeman's arrival with "comes... another...". Freeman uses his Long Jump Module to traverse the floating islands of Xen, encountering many of the aliens that had been teleported into Black Mesa in their natural habitats, as well as the remains of HEV-wearing researchers that came before him. Freeman arrives at a large central island, and within finds a small portal, which he steps into and is teleported to the Gonarch's lair.[19]

Hl nihilanthcrystal

The Nihilanth battles with Freeman on Xen.

Freeman battles and defeats the Gonarch and her Headcrab minions.[68] He continues his journey across Xen, with supplies running short, wasted on destroying the Gonarch. Freeman traverses an expansive series of Xen islands, coming in contact with many Xen hostiles, and eventually finds himself in an Alien Grunt cloning facility. Within the factory, enslaved Vortigaunts are forced to work, but do not attack Freeman, perhaps to subtly rebel against their masters. After much fighting and interception from Alien Grunts and Controllers, Freeman comes across a large, ominous portal on a lone series of floating islands.[69] Upon entering the portal, Freeman is faced with the Nihilanth; the holder of the interdimensional rift, the one responsible for the enslavement of the Vortigaunts, and leader of Xen forces.[70]

G-Man end 2

The G-Man addresses Freeman on Xen.

Freeman engages the Nihilanth in its lair. As he battles the creature, it teleports him to several sub-caverns filled with Xen creatures. Freeman continuously escapes these caverns, and destroys the Nihilanth's shield, allowing him to destroy its vulnerable brain. As the creature dies, it floats toward the ceiling, and explodes in a giant green blast that overpowers his senses.[70] When he comes to, he is confronted by the G-Man, who had stripped Freeman of all his weapons while he was unconscious under the excuse that "most of them were government property", but states "As for the suit, I think you've earned it". Both are transported to various locales around Xen, while the G-Man praises Gordon's actions in the border world. He explains that his "Employers" agree with his assessment that Gordon has "limitless potential" and have authorized him to offer Freeman a job. The final teleportation takes Gordon to the same tramcar that he rode in on the morning of the experiment, but apparently flying through space at immense speed. Gordon accepts this offer by stepping through a portal, and, finding himself floating in nothingness, hears the G-Man's voice one last time: "Wisely done, Mr. Freeman, I will see you up ahead...".[71]


BME newspaper clips

Newspaper clippings on a cork board in Eli's lab, revealing some plot information, and mentioning the Seven Hour War.

Main article: Seven Hour War

The consequences of the Black Mesa Incident were massive. The relatively small inter-dimensional rift caused Portal Storms to rage across Earth, bringing large amounts of Xen wildlife to the planet. Earth governments set up protection centers across the planet as they tried to deal with the hostile aliens. The continuing portal storms and dimensional fluctuations attracted the attention of the Combine, an immense inter-dimensional empire that was responsible for chasing the Nihilanth and its minions to Xen in the first place.

The Combine mounted a full-scale assault on Earth, and the United Nations declared war on their attackers. The Combine completely overwhelmed Earth's military forces and smashed all opposition in the Seven Hour War. The Combine held position over United Nations headquarters in New York City, and former-Black Mesa administrator Wallace Breen negotiated a surrender at the expense of humanity's freedom. Dr. Breen was then appointed as Earth’s administrator, a role with powers akin to a dictator on the behalf of the Combine Empire while an alien race will be overseeing all activities and communication between Earth and the Combine - the Combine Advisors.[72] The death of the Nihilanth also ended the slavery of the Vortigaunt race, earning Gordon Freeman their eternal gratitude.[73] Dr. Eli Vance convinced the Vortigaunts to side with humanity against the Combine, and the two species formed an underground resistance aiming to overthrow their alien oppressors.[73]

Although the incident is largely considered to be a terrible accident, there is incidental evidence which suggests it is to some extent engineered. The Nihilanth seemed to have been planning the invasion from Xen for some time,[70] and the G-Man more than once hints at his own manipulations of the affair, most notably when he whispers to Eli Vance just before the Resonance Cascade to "prepare for unforeseen consequences".[28] To what extent either of these individuals were involved in the authoring of the incident is currently unknown. Adrian Shephard's diary entries also seem to suggest that the event is planned to a degree, as Shephard and the HECU are training and preparing for the mission to Black Mesa a week before the incident even happens.[74] By the time of Half-Life 2, the Black Mesa Incident may have been somewhat well known, as it was mentioned in a Breencast. The scapegoat for the incident being Gordon, as Breen stated some of the "worst recesses" of the Black Mesa Incident had been laid directly at his feet. While in part this is true, there were a variety of factors and even personnel who played a part in the incident's occurrence.

Known survivors[]

List of appearances[]


  • In Half-Life 2, the mishap of Lamarr damaging and malfunctioning the teleport that Gordon was about to use near the start of the game is an echo to the Black Mesa Incident.


    • Characters hint to sometime in March
    • Sometime in December according to Opposing Force Chapter 1, Welcome To Black Mesa
    • Possible years: 2000-2009
  1. 2.0 2.1 2.2 Half-Life: Opposing Force; chapter Conclusion
  2. Quarantined by the G-Man
  3. Assuming every Apache seen is unique. Does not include Half-Life Decay yet
  4. Assuming every Osprey seen is unique
  5. Assuming every F-16 seen is unique
  6. Counting all confirmed deaths in scripted events, zombies, and corpses that are visibly seen. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  7. Assuming all Barnacles encountered have consumed at least 1 Black Mesa employee that they spit out on their deaths. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  8. 381 is the confirmed total number of Black Mesa personnel we see, both living and dead, from the start to the end of each game. This figure assumes all these personnel perished. The upper figure includes all Barnacles encountered. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  9. Counting all confirmed deaths in scripted events, zombies, and corpses that are visibly seen. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course. This figure also includes crews for destroyed vehicles - 2 for the Apache and Osprey, 3 for the Bradley, and 4 for the M1 Abrams. Does not include troops that deploy from Ospreys, as they can deploy indefinitely until the vehicle is destroyed.
  10. Assuming all Barnacles encountered in chapters where HECU troops appear have consumed at least 1 HECU soldier they spit out on their deaths.Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  11. 393 is the confirmed total number of HECU personnel we see, both living and dead, from the start to the end of each game. This figure assumes all these personnel perished in the nuclear explosion. The upper figure includes all Barnacles encountered in chapters where HECU troops appear. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  12. All Black Ops troops encountered during the game - also includes the crew of the Apache shot down in Opposing Force
  13. Assumes all Barnacles encountered in chapters where the Black Ops appear have consumed at least 1 Black Ops trooper they spit out on their death. Includes figures from Half-Life, Opposing Force, and Blue Shift. Does not yet include Decay - these figures will be added in due course.
  14. Does NOT count Xenian wildlife. This figure includes only footsoldiers of the Xenian forces; Vortigaunts, Gargantuas, Grunts, Controllers, and the Nihilanth
  15. Does NOT count Race X wildlife, only counts Shock Troopers as they are the footsoldiers of the Race X forces, and the Gene Worm
  16. Half-Life: Blue Shift
  17. 18.0 18.1 18.2 18.3 Half-Life chapter Lambda Complex
  18. 19.0 19.1 Half-Life chapter Xen
  19. 20.0 20.1 Half-Life: Opposing Force chapter Crush Depth
  20. Half Life chapter Anomalous Materials
  21. Half-Life chapter Apprehension
  22. Half-Life scientists: "Any ideas on the origin of that new sample?"
  23. Half-Life: Decay chapter Dual Access
  24. Half-Life PlayStation 2 instruction manual
  25. Half-Life chapter Anomalous Materials
  26. 27.0 27.1 27.2 Half-Life: Decay chapter Dual Access
  27. 28.0 28.1 28.2 28.3 28.4 Half-Life 2: Episode Two chapter Our Mutual Fiend
  28. Half-Life: Decay chapter Dual Access
  29. 30.0 30.1 30.2 Half-Life chapter Anomalous Materials
  30. 31.0 31.1 Half-Life: Blue Shift chapter Insecurity
  31. Half-Life chapter Black Mesa Inbound
  32. Half-Life chapter Anomalous Materials
  33. 34.0 34.1 Half-Life chapter Unforeseen Consequences
  34. Half-Life: Decay chapter Surface Call
  35. 36.0 36.1 36.2 36.3 Half-Life chapter We've Got Hostiles!
  36. Half-Life: Decay chapter Surface Call
  37. 38.0 38.1 Half-Life: Opposing Force chapter Incoming
  38. Half-Life: Blue Shift chapter Duty Calls
  39. Half-Life: Blue Shift chapter Captive Freight
  40. Half-Life chapter Office Complex
  41. Half-Life: Decay chapter Resonance
  42. Half-Life: Decay chapter Domestic Violence
  43. Half-Life chapter Blast Pit
  44. Half-Life chapter Apprehension
  45. 46.0 46.1 Half-Life chapter On a Rail
  46. Half-Life chapter Power Up
  47. Half-Life: Decay chapter Rift
  48. 49.0 49.1 Half-Life: Opposing Force chapter Friendly Fire
  49. Half-Life: Decay chapter Xen Attacks
  50. 51.0 51.1 51.2 51.3 51.4 Half-Life: Blue Shift chapter Deliverance
  51. Half-Life chapter Apprehension
  52. Half-Life chapter Residue Processing
  53. Half-Life chapter Questionable Ethics
  54. 55.0 55.1 55.2 Half-Life chapter Surface Tension
  55. Half-Life chapter Forget About Freeman!
  56. Half-Life: Opposing Force chapter Welcome to Black Mesa
  57. Half-Life: Opposing Force chapter We Are Pulling Out
  58. Half-Life: Opposing Force chapter Missing In Action
  59. Half-Life chapter Forget About Freeman
  60. Half-Life: Opposing Force chapter We Are Not Alone
  61. 62.0 62.1 Half-Life: Opposing Force chapter Vicarious Reality
  62. 63.0 63.1 Half-Life: Opposing Force chapter Worlds Collide
  63. Half-Life: Opposing Force chapter Pit Worm's Nest
  64. Half-Life: Opposing Force chapter Foxtrot Uniform
  65. Half-Life: Opposing Force chapter The Package
  66. Epilogue of Half-Life: Opposing Force
  67. Half-Life chapter Gonarch's Lair
  68. Half-Life chapter Interloper
  69. 70.0 70.1 70.2 Half-Life chapter Nihilanth
  70. 71.0 71.1 Half-Life chapter Endgame
  71. 72.0 72.1 72.2 Half-Life 2 chapter Black Mesa East
  72. 73.0 73.1 Half-Life 2 chapter Water Hazard, the All-Knowing Vortigaunt speech
  73. Half-Life: Opposing Force instruction manual
  74. 75.0 75.1 75.2 75.3 75.4 Half-Life 2 chapter Point Insertion
  75. Half-Life: Opposing Force chapter We Are Pulling Out
  76. Half-Life 2 chapter Route Kanal