Cyber-Leader Jarl was a CyberMondan from the planet Mondas, and was a member of the second Cybermen force which invaded the Snowcap Base in Antarctica in December 1986 with the intention of detonating a Z-Bomb in its missile silo.

Jarl, Regos Krang and another Cyberman went to try and get into the Z-Bomb silo but were weakened by radiation used by Haines and John Dyson. The weakened Jarl was then shot and killed by Ben Jackson. (TV: The Tenth Planet, PROSE: Doctor Who and the Tenth Planet)