Imbreus was one of the Thessalioi. The best known story about the Thessalioi Kentauroi is when they and one Kentaurid named Hylonome were invited to attend the wedding of their half-brother Peirithoos, the Lapith king. The Thessalioi Kentauroi became drunk and attempted to carry off the bride and the female guests. In the battle which ensued the Kentauroi were all but wiped out. Most likely Imbreus was among the number killed.
Nephele & Ixion