All information is currently partial and will be corrected in the future.

The boss is same as TFB only red.

To spawn:

http://www.twitch.tv/thinmintz/c/2693934

-The boss is where everybody though it would be, up the stairs between Titan and Thrasher.
-16 NiM (not sure if possible in HM)
-Kill the group up the stairs making sure they all die at the same time (will get a buff at cca 20% same icon as Mind Crush), the ground will shake and a shadow will appear
-Use orb to spawn an orb which will hurt the channeller (heal him)
-After channel hateful Entity will spawn
-Currently unlimited attempts

Fight:
-Base mechanic is same as TFB, mask required
-Switching damage dealt buffs and damage reduction buffs
-Pulls people in periodically
-Death Mark 2s cast - cleansable, essentially a time bomb, when it runs out you die, 5s to cleanse.
-Bunch of other player targeted debuffs, most likely all bad.