The Decepticon/Predacon Alliance is, perhaps unsurprisingly, a coalition of the Decepticon and Predacon factions. Very little is known about it. No reference is made to it as of the timeframe of Beast Wars; in fact, Ravage specifically identifies himself as representing "the Predacon Alliance", perhaps implying that whatever organization once guided both factions is now solely in the hands of the Predacons.
The Tripredacus Council may have been the heads of the Alliance; they were certainly involved with it. Known dissenters from the Alliance include Decepticon general Deathsaurus and Predacon criminal Megatron. Descent Into Evil