Headcrab Shells are a form of biological weaponry used by the Combine. These shells are launched over long distances and land in enemy-controlled territory, releasing a payload of Headcrabs. Used primarily to flush out and destroy Resistance bases, they are responsible for the destruction of many communities. The shells themselves seem to be a type of mortar or artillery, packing an explosive charge as they land. As such, empty shells are also seen being used as conventional artillery by the Combine to destroy entrenched positions or buildings.
These large projectiles can crash through most barriers, embedding themselves several feet, even into concrete. The impact alone can kill or injure any persons too close to the crash site. At this point a hatch at the rear of the shell opens and releases multiple Headcrabs. There are several hoses that seem to spray the Headcrabs with some sort of gas or mist. Usually these are only basic Headcrabs, although Fast Headcrabs have also been observed exiting a shell. Poison Headcrabs also seem to be used in shells, but have only been seen emerging from unlaunched Headcrab Shells during Lost Coast and in the chapter Exit 17 of Half-Life 2: Episode One, in which only one Headcrab is included per shell. In Half-Life 2, the player can enter a house during the chapter Highway 17 which has been bombed by a poison Headcrab Shell. Searching the house will reveal several poison Headcrabs and a poison zombie, but no other types, indicating that the shell contained poison Headcrabs.
The Headcrabs released by the shell will infest the surrounding area. This happened to the Resistance's mining town of Ravenholm prior to the events of Half-Life 2 which were inhabited by a large number of escapees from City 17 and was quickly overwhelmed by the parasites, to the point where there is only one known human survivor, Father Grigori, left in the town.
Throughout Half-Life 2, Headcrab Shells are fired from an unseen launcher somewhere in the player's vicinity. In Lost Coast, a working launcher is seen in St. Olga's monastery. The Headcrab Shells are fired with a loud explosion and streak towards their target in a steady arc, leaving temporary vapor trails behind and emitting a noise not unlike a conventional mortar shell.
The launcher itself has a large metal barrel with a plunger inside which fires Headcrab Shells roughly every 10 seconds. A sign on it indicates, "Warning, Moving parts can crush and cut. Keep hands and other objects clear during operation." It is easily destroyed by dropping metal objects like candlesticks into the chamber.
In the Half-Life 2 chapter Water Hazard, Headcrab Shells can be seen toppling a massive brick factory chimney, almost crushing Gordon in his airboat. The initial explosion allows the shell to penetrate buildings with ease, as is shown by their use during The Uprising in City 17.
Since the Headcrabs are effectively bottle-necked into the opening, they can be defeated easily before they are able to climb out of the shaft by simply standing near it and shooting or beating them to death as they jump out.
On one side, the Shell has an arrow with "DANGER" and "KEEP AWAY" written above and under it.
Behind the scenes
- The concept was first intended for the cut Sacktick and as a device attached to a Gonarch, the Big Momma Pod.
List of appearances
- Half-Life 2 (First appearance)
- Half-Life 2: Lost Coast (Non-canonical appearance)
- Half-Life 2: Episode One
- Half-Life 2: Episode Two