The Doomseekers are a faction within the House of the Forsaken that have as their goal the creation of a biological Doomsday weapon
A loose organization of those touched by the elemental plane of Smoke to combat the PCs
The Floating World, the domain of the Hikikomori
The PCs find a strange helmet, when donned it will take control of that PC and speak and act trough him/her. It explains that it is benevolent and needs their help in a quest and that it will stop possessing the PC when the task is done. Great if a player is gone for a number of sessions.