The Viper King, or Subject Gamma, is a unique alien enemy encountered in the Alien Hunters DLC for XCOM 2.

He is a special, and far more powerful, Viper alien and is the first and weakest Alien Ruler to be encountered.

Like other rulers, he performs one action after every action made by any XCOM squad member, during a special "Ruler Reaction" phase.


  • He can use Tongue Pull like other Vipers, binding a soldier with a fifty percent chance to knock them unconscious with every tick.
  • As others Vipers, he can also use an area-of-effect breath ability but instead of poison, he spits out a cloud of gas which freezes units caught in it for two turns.
  • He will summon a psionic rift after a few turns, or after taking too much damage, and attempt to escape. If he does so, XCOM will encounter him again in a future mission, with the remaining health he had when he escaped.


  • Completing the Viper King Autopsy unlocks the Serpent Suit, an armor based on his appearance and abilities.
  • He is the first and only male Viper encountered.
    • Once killed, the description mentions that he was already reproducing with the female Vipers, despite being only recently hatched.
  • There is a glitch where if you kill the Viper King the mission you encounter him, you will not get the corpse.
  • Ending turns will not trigger the defrost tick on Alien rulers. This makes it possible to completely shut down a ruler by only attacking with Lightning Hands and ending turns to refresh the cooldown.