Creature of P2X-338
Marduk's priests placed the wicked tyrant into a sarcophagus with this creature, which continually devoured him as the sarcophagus rejuvenated his organs countless times. When the Goa'uld could no longer bear the unending torture it left the host's body and sought refuge in the creature itself, living within it until the sarcophagus was opened by a Russian Stargate unit.
When the creature was wounded by SG-1, the Goa'uld inside abandoned it for another human host: Major Vallarin of the Russian unit. The creature died soon after.
The Tomb - SG-1 and their Russian team learn that a previous Russian unit opened Marduk's sarcophagus, releasing a deadly creature.