The Bankikai (万鬼会, lit. 10000 Ogre Group/The Demon's Society) was a group of In-Birth who were lead by Ogre. They were shortly disbanded after a battle with Amnesia.
While it is unknown exactly as to when the faction was founded, Bankikai expanded at an incredibly fast rate, fast enough for both Amnesia and Licht Kreis to notice. Seeing Amnesia as an enemy, the group called out to them for a fight. This fight turned out to be their undoing as their leader, Ogre, was fatally wounded in a fight with Hilda. Things also went from bad to worse as the fight took place during a "Quickie" or "QKY" for short, leading to a freak accident which led to Roger of Amnesia to transform into a Void, finishing off Ogre and for one of the co-leaders, Zohar, going insane.