The Gene Worm is the final boss of Half-Life: Opposing Force, and the most mysterious of the Race X aliens. This life form is said to be the equivalent of a "biological resource management factory." It is suspected to be capable of taking any of Earth's natural resources and assimilating it to make them useful to the aliens' needs. If one fully entered Earth and became productive, he would effectively alter the planet enough to become useful as a new homeworld for Race X. However, this was never shown in action.