Abbey of the Burning Tomb
This white abbey is in the land of Gore.
Malory, however, not only never describes the actual killing, which is not unusual: Malory has many characters, including Tristram, killed "offstage" - but also resurrects Bagdemagus during Arthur's war with Lancelot. Sommer failed to find Gawaine's alleged slaying of Bagdemagus actually described in the Vulgate manuscripts, either.
More important than Bagdemagus' tomb, in this same abbey is a burning tomb wherein a soul in torment has been waiting 354 years for Galahad to release him from the punishment he had incurred for sinning against Joseph of Arimathea - apparently some sort of private purgatory.
Abbey of the Adventurous Shield | The Legend of King Arthur