Sarpa are the lizard-like forms of the Watchers, and are found residing in thge Monolith, as well as the pilots to the Knights and Archon tanks. They tend to slither along the ground, leaping at their prey and using their long claws to lash at them. Watchers start out as larvae (which look like a cross between a snake and a slug), slowly evolving with each passing year. Eventually, they grow a tail and membranes running between their arms and their bodies.
It is revealed in the third Episode of the game that Watcher Elders have the ability to shapeshift. It is also shown that Elders do not wear robotic suits, as they do not participate in combat, and therefore do not need these suits.
Outside of their robotic suits, organic Watchers are nowhere near as agile or flexible, and their only attack outside of their suits is to pounce on you. This sometimes leads into a QTE (quick-time event) in which you must move the movement analog stick left and right in order to throw them off (this only occurs with the Watchers that have membranes and tails).