Shapeshifter

A shapeshifter is a person which is able to master his appearance and change into a different form.The best knolwn shapeshifters in Middle-Earth are the Skinchangers of the Beornings but the skill of shapeshifting is also common among the Ainur, both Dark Lords, Morgoth and Sauron were able to assume different forms, Morgoth appeared as a huge Giant when he entered Arda and later as a terrible Warlord, but when he went to seduce the Hildor he took the shape of a mighty and beautiful man.Sauron appeared as a mighty and beautiful fire spirit, in his original form and in his disguise as Annatar but also as a terrible demon or Warlord, as a Serpent, a Werewolf and a Vampire.The Sky-spirits of Manwe and Elbereth -the Manir and Suruli- also appeared both as human-like beings and in the form of Birds.Morgoth´s Phantoms, whom he sent out as Agents and Spies even could appear in any form. The Istar Radagast also was a famous "Master of shapes and hues".

shapeshifters in MERP
There are other shapeshifters than just the beornings in MERP, among them are the:
 * the Drelic Monks of Ereg Eiren
 * the high-priestess of Benish Armon.
 * Scara-Hai-Orcs
 * some maiarin Werewolves and their half-maiarin offspring.
 * the Wereworms