A Superunique is a specific kind of monster in Diablo III. They are displayed with their names in purple, have set spawn locations, and are often part of a quest or event. They will have special attacks such as Vampiric, Knockback and Jailer. While some superuniques are always found on given locations (e.g. [[Odeg the Keywarden]] always appears somewhere in the [[Fields of Misery]]), other others only spawns spawn occasionally. The probability of finding some is really low and encountering them can require hundreds of attempts. This is why the "A Unique Collection" achievement is one of the hardest to complete in Diablo III.