Orion: Ground Zero by StealthToast
Orion: Ground Zero is a 2-player coop altered melee map featuring 6 unique subfactions to choose from to go up against 6 Zerg Broods, each with their own techtree and specialties. The objective of the map is to gather an amount of Crimson Minerals and destroy sufficient enemy Broods. In order to do this, you have to keep a balance between offense and defense, take advantage of control points, know when to call in support powers to aid you and secure strategic areas in the map to hold the enemy off more efficiently. The map lasts, on average, for 30-60 minutes. It varies depending on the selected difficulty however.
I've played this and beat it before but once you beat it there is very little replay-abillity afterwards