BBY/ABY is used to position items along the Star Wars Timeline. BBY refers to Before the Battle of Yavin. ABY refers to After the Battle of Yavin. The Battle of Yavin in Episode IV: A New Hope occured in 0 BBY/ABY.
With his Shadow Collective army stalled, Darth Maul calls on Mother Talzin for help and is sent reinforcements-the deadly Nightbrothers! Maul is ready again to take on the Separatist droid army, Count Dooku, and General Grievous, in a trio of simultaneous battles!