Gudrun Tyburn is an immortal sorceress of the Marvel Universe, a member of Mys-Tech. The group gained its immortality in 987 through a pact with Memphisto. The pact depends on the sorcerers providing the Hell Lord with a steady supply of souls. This has not prevented them from researching ways to doublecross Mephisto over the last millennium. The nature of the spell connects their life to reality around them. Nobody can kill them but Mepisto.
Gudrun was hinted to be the mother of Dark Angel/Shavaun Haldane but the subplot was never resolved.