Alexsandr Kallus

Agent Kallus (codenamed ISB-021) is the main antagonist of the first and second season of Star Wars Rebels, later a secret ally in Season Three. He is an Imperial agent of the Imperial Security Bureau, assigned in making sure that everyone remains loyal to the Empire and anyone who shows any whiff of disloyalty is eliminated.

His primary objective is to hunt Rebels, investigate any sort of incidents that could spark a Rebellion again the Empire. He is also skilled in actual combat and rather than leading an attack from afar, he involves himself in the field.