First Prime
From The Stargate Omnipedia
A Goa'uld's foremost Jaffa warrior, in command of his army and charged with carrying out his most important tasks. Ra's First Prime was a Jaffa who wore the head of Anubis. Apophis's First Prime was Teal'c, until he rebelled. Bra'tac has also served as First Prime of Apophis, and of Klorel.
KEY EPISODES
Children of the Gods - Teal'c gives up his position as First Prime of Apophis and rebels against his enslaver, firing on his own men.
Threshold - In a dream-like state, Teal'c recalls his rise to the rank of First Prime under the careful tutelage of Bra'tac.
The Warrior - Kytano, who claims to have been first prime to the slain Goa'uld Imhotep, leads the rebel Jaffa -- until Teal'c reveals that Kytano is not Jaffa, but Imhotep himself.