D&D 3.0: Tales from Mystara
The Sacred Mummy is a Mummy found on the ruins of Port Siers, around 100 years after the entire population was killed by volcanic ash, this unidentified mummy was found by a group of adventurers trying to rob a tomb. A group of priestesses of Elegy Island with their Makai servants were at that moment on Ierendi City and used their skills and magic to capture the dangerous mummy. They study the tomb and discovered something that makes the mummy important to them.
With the proper permits and transportation, the mummy was taken to Elegy Island with the artifacts from its tomb. The mummy is part of the undeads used as protection on the Island by the Death Kahuna.