Shrak for Quake (1997)

Humanity has lost control over Earth... Mutants that were created during previous conflicts have completely gotten out of control. Humans were forced to flee from the planet and watch from the Moon as their home was overrun by mutants and the ones who joined them. Now, the situation has become even more dire. Unorganized mutant actions have became organized – someone or something named "Shrak" has united them and started rebuilding Earth as a gigantic military base. You were sent back to Earth in order to perform reconnaissance on "Shrak" and its army and report back. Except that your ship has crashed and will not be flying you back anytime soon.