Lord Guerreiro was the Dark Lord of the Decreton Empire from 18 BBY up until his death in 40 ABY. He was killed by Jasca Ducato after he attempted to turn him to the dark side of the Force. Ironically, he succeeded, but at the cost of his own life. The Sith Master of an unnamed Sith apprentice and Darth Wyyrlok, Guerreiro ruled the empire with an iron fist, favoring certain Sith Lord's over others.
Following his death, Wyyrlok was noted as saying that, had Darth Abeonis not killed Guerreiro and gone to war with the Sith Order of Decreto in 42 ABY it was likely the empire would have erupted into another civil war as a result of Guerreiro's favoritism.