The Tok'ra symbiote within Martouf, and the mate of Jolinar of Malkshur for over one hundred years. Lantash was very passionate in his ideas, often to the point of anger. He possessed a great love for Samantha Carter, who had been the last host of Jolinar before she died. Over time, he came to love her as much as he had loved Jolinar.
Lantash and Martouf complimented each other in the way they handled situations. Martouf always carried a cooler head, but Lantash possessed a fire to attain their goals and to get the job done. But unbeknownst to Lantash, Martouf had become a za'tarc, an individual secretly transformed into a Goa'uld assassin, and was killed by Carter when his programming forced him to try and kill the President of the United States. However, Lantash survived. He was removed from the body and placed in a stasis container.
Nearly two years later, he was still very week and recovering on the Tok'ra's primary base on the planet Revanna. When the Goa'uld attacked and bombarded the base, his container was destroyed. To save both himself and the new S.G.C. recruit Lieutenant Elliot, he blended with the young man to keep them both alive. Lantash's knowledge became invaluable as both he (within Elliot) and SG-1 journeyed far from the Tok'ra base using underground tunnels, trying to avoid the invading forces.
Lantash and Elliot gave their lives to save the rest of the team when they realized that Lantash did not have the strength to repair Elliot's injuries and save their lives. Elliot / Lantash were given a vial of symbiote poison, powerful enough to eliminate the entire occupied force, and, presumably, used it on them to allow SG-1 and Jacob Carter to escape.
The Tok'ra, Part 1 - Martouf/Lantash are saddened when they learn the final fate of Jolinar, but comforted to learn that a part of her remains within Samantha Carter.
The Tok'ra, Part 2 - Martouf/Lantash console Carter as she helps her father make the decision to become a Tok'ra host.
Serpent's Song - Martouf/Lantash arrive at the S.G.C. to counsel them on the grave decision they have made to keep Apophis from Sokar.
Jolinar's Memories - Martouf/Lantash join SG-1 on a mission to recover Jacob/Selmak from Sokar's prison moon of Ne'tu.
The Devil You Know - Martouf/Lantash successfully recover Jacob/Selmak, after being tortured by Apophis with their memories of Jolinar.
Divide and Conquer - Martouf is discovered to be a za'tarc -- a brainwashed assassin -- and Lantash is nearly killed when his long-time host is shot dead.
Summit - Lantash remains in a stasis container on Revanna, still weak from Martouf's death. When the vessel is destroyed, he blends with Lieutenant Elliot to keep them both alive.
Last Stand - Lantash and Elliot sacrifice themselves to allow the rest of the group to escape an army of Jaffa that occupy Revanna, by allowing themselves to be captured before releasing the Tok'ra's deadly symbiote poison.