Assimilator

Assimilators are bizarre Scrin infantry units that perform functions analogous to human Engineers. Assimilators have been clearly seen to capture and repair buildings. Any buildings captured are immediately converted to serve the Scrin. Assimilators may also recover fallen walkers, namely the alien Annihilator Tripod and human Avatar and Juggernaut, restoring them to combat functionality in order to fight for the Scrin.

The sole advantage that the slow-moving Assimilator seems to possess over our own Engineers (and Saboteurs) is its ability to become stealthed when not moving. This has been known to have certain tactical advantages for the aliens.