The Avatar of Fear (aka Cazic-Thule) is located in the cave that has the entrance to the shard of fear zone. He's a nasty level 88x4 epic creature that will constantly cast fear attacks on the raid group and possibly stun/stifle attacks. Like the other avatars he has one consistant buff on him throughout the fight and has a buff on him that raises health + physical mitigation.

Having gear from the Shard of Fear that grants resistances to fear can really help out during the fight. It is best to treat this fight like a higher end version of Druushk who would constantly cast AoE fear attacks. The Crusader endline AA ability is also useful since it grants permanent immunity to fear effects.