Karm's planet of origin is unknown. However, at some point it was conquered by the forces of Ming. Recognized as having a brilliant scientific mind, Karm was subsequently spared and brought to Mongo to work in Ming's laboratories and to help develop weapons of mass destruction.
Although Karm undertakes such work and feigns loyalty to Ming, he has constantly been looking for opportunities to escape this wretched fate. He secretly prepares a clever disguise and quietly learns what he can about Ming's other various scientific projects, including the sources of his power. At some point he befriends another fellow scientist named Druk, who is also held prisoner.
With Ming meeting little resistance in his quest for universal domination, Karm's prospects look bleak until the Earthmen Flash Gordon and Doctor Zarkov arrive on Mongo and bring a fierce retaliation to Ming's very doorstep. When Zarkov is captured and put to work in the lab, Karm befriends him and shares what he has learned. Karm also gives Zarkov his disguise, allowing him to escape while he himself bravely volunteers to stay behind and remain a prisoner.
For a while Karm remains trusted by Ming who has him work on the production of deadly Zoltranillium projectiles. However, Karm's treachery is exposed when Sonja discovers Dale Arden secretly contacting him. Ming seems more disappointed than angry, suggesting a genuine respect for the man, but still has him thrown into prison. Karm still harbors hopes of freedom, especially as Princess Aura and Captain Sudan help him maintain communication with his friends on the outside.
Karm's life is ended brutally. Brought before Ming, the gentle scientist reaches breaking point when he witnesses the distress of Princess Aura and launches himself at the Emperor in a noble but futile attack. Ming is prepared for such an assault and draws a knife on the unfortunate Karm, much to the horror of the watching Aura.
Nevertheless, Karm was to have the last laugh. The information he revealed to Doctor Zarkov was ultimately to prove pivotal in bringing about Ming's eventual downfall.
Karm was portrayed by actor Michael Mark.