Leymac and his host Marik were the leaders of a team of Tok'ra that worked in the SGC in 2008 and took part in Ba'al's Extraction Ceremony. Leymac often noted that if it would save Egeria he'd be willing to sacrifice himself so she could take his host.
After Marik's actions resulted in the kidnapping of Dr. Carolyn Lam and the theft of the Time Jumper, Leymac took control when he, Marik and Lam were rescued from the sarcophagi on Ra's Ha'tak. Leymac helped guide the team to where the Time Jumper was and argued with Lam about her unwillingness to follow Marik's directions.
Following the rescue, Marik and Leymac were imprisoned on the orders of the Pharaoh Hor-Aha and their help in fighting against Ra was rejected as they were thought to be too untrustworthy. Following the defeat of Ra, Marik and Leymac were returned to 2009 in the Time Jumper to face punishment for their actions. (SG1: "Moebius Squared")