Brain

The First Alien War is conducted at the command of a single creature: a gigantic alien brain residing in Cydonia. If X-Com is able to find and neutralize this creature, the alien assault will be dealt a mortal blow in leadership and morale.

Residing in a large antechamber, the Brain is 2x2 spaces in size, and requires 40 damage to injure, following the rules for Destroying Terrain. While large, the Brain is fragile, and even damaging a fourth of the creature is enough to kill it.