The Warbringer was a powerful protoss reaver. Compared to a regular reaver, it was much tougher, and all reaver upgrades were default on Warbringer.
In addition, it attacks immediately, instead of waiting before attacking like an ordinary reaver.
The Warbringer was captured by Schezar's Scavengers and placed in a stasis cell on Aiur. Protoss Praetor Mojo enlisted the help of a breakaway faction of Alpha Squadron, a military unit within the Terran Dominion, led by Tom Kazansky and Magellan. The terrans rescued Mojo, the Danimoth and the Warbringer from captivity.
The Warbringer took part in a mission to destroy a cerebrate captured by the Scavengers, alongside Mojo's Boys and the breakaway terran faction. The mission was a success.