"Elfslayer" was the name given to a doppleganger-like creature that committed a string of murders around the elven city of Fairport. The creature went unnoticed for years, taking the guise of its victims and feigning their departure.
The creatures activities were uncovered when a party of dark elves attacked the village it was hunting in. When adventurers Nawen Jadie and Riddil Halfelven showed up at the behest of the priest Aust Liadon, Elfslayer had already butchered the drow and had moved on to other prey. Taking the guise of Aust's Father, Evindal Liadon, the recently killed high priest of Solonar, Elfslayer attempted to murder the trio of adventurers, fleeing to an ancient orc fortress once the element of surprise was lost. The adventurers chased him into the fortress where they were unable to strike the final blow. Elfslayer escaped into the nearby foothills.
Upon returning to the village, the adventurers found that it had been destroyed by a second party of drow.
Elfslayer was very similar to a doppleganger, with the addition of supporting four displacer-beast-like tentacles from its back. Unlike ordinary dopplegangers, Elfslayer could take non-humanoid forms and could attack some of its victims under the guise of wild-animals.