Hydra

The Hydra is one of various enemies cut from Half-Life 2 during the later stages of the game's development. It was originally supposed to be a large underground entity that had numerous tentacles that went up to the surface. The tentacles were neon blue, slightly transparent and were capable of piercing through prey, such as a Combine Soldier in the trailer. The Hydra was made of gelatinous flesh, with organs clearly visible. The Hydra does not seem to want to eat Humans and and Combine troops like Antlions do, they would seem to just like killing things

This enemy was cut from the game for a variety of reasons, including coding difficulties, that its AI proved troublesome, and that &mdash; while it looked impressive &mdash; it wasn't very fun to fight.

Close look at some maps from the 2003 leaked Half-Life 2 Beta suggests that the Hydra was somehow planned to be a boss and the end of the levels now included in the Half-Life 2 chapter "Route Kanal".

Its shape might have been inspired from the Tentacle in the original Half-Life.