Nothing spawns out of the enemy base at first. After a short while, Galactic Overseer Nyandam appears, along with Those Guys, B.B.Bunny and Squire Rel serving as peons. Awhile after, Bore will be spawned, with Razorback following soon after.
Despite Nyandam being the boss, the main threats here are the Bores, especially Razorback. Make sure of bringing units to slow or freeze them. Also, try to kill the red bore quickly, or else you'll have to fight Bore and Razorback together, making the battle nearly impossible.