Lacertus was Feeorin Sith Lord of the Sith Order of Decreto and a leading member of the Proelicitia; considered by many to be Setal-ni's second-in-command.
The only Feeorin Sith Lord of his age, Lacertus was an apprentice of Konopka are one of his most promising students; and as such was chosen for membership in the Proelicitia following an unsuccessful attempt on Setal-ni's life in 3,963 BBY. Lacertus was later present at the Battle aboard Knightstar, personally decapitating Corae.