Basilisk

Basilisk
Being the easiest to get alien unit besides the dretch, the basilisk is considered relatively weak, but it's got some nice tricks up it's sleeve. The Basilisk is the only evolved alien combat unit that can wallwalk, but unfortunately has the least health and weakest attack of any of those units. However, when touching a human, they become "grabbed", which means they cannot turn around. If the Basilisk catches an enemy alone and manages to get behind him while "grabbing" it, the Basilisk can easily kill the human.

Adv. Basilisk
The Advanced Basilisk has slightly more health then the normal basilisk, but more importantly, get an poison spray attack, which he can use to poison enemies. The attack rate of the Advanced Basilisk is also slightly increased.