The Heart of the Udyrfrykte is a quest item found in the The Elder Scrolls III: Morrowind expansion Bloodmoon.
The quest item is needed for The Mead Hall Massacre. It is identical to a Daedra's Heart in terms of appearance and effects.
Trivia
- In The Elder Scrolls V: Skyrim there is an unique Troll named Udefrykte, located in the Dawnstar Sanctuary.