The following section contains information from StarCraft: Retribution.
The Fragile Alliance was a zerg and protoss force active during the Great War. The faction was led by a cerebrate and its zerg brood on Aridas. The cerebrate possessed xel'naga technology found in ruins on Aridas which let it enslave a small protoss tribe. The alliance was broken when Terran Dominion forces led by Jenson Archimedes and a terran commander destroyed their base and incapacitated the cerebrate, and destroyed the protoss and zerg bases that took part in the alliance.