Barrier Servitors. Final Barrier Servitor doesn't spawn in the boss room if you kill the boss fast enough.
Heavy Shank in boss room.
A few Void Servitors.
Arach-NO! – When defeated, Fallen Vandals spawn a web mine at their feet.
Boss appears after you kill the ads and Heavy Shank. You can prevent the third Barrier Servitor and a wave of Exploder Shanks from spawning if you kill the boss fast enough.