>>43333364- Rogal Dorn isn't dead. Somehow, in the confusion of WEs' Zerg rush, he got dropped into the Warp where he'd been Draigo-ing for a while before finding the Imperial Palace from the wrong side, the wrong side being the Warp rift Magnus ripped open. He's now fighting in Palace's basement alongside Custodes etc and can't leave because opening the door would let daemons inside.
- at some point, Russ and Corax, both in the Eye of Terror, bumped into each other and are now travelling the Eye together
- as the Emperor's psyche shattered from his time at the Golden Throne, very tiny shards manifest from time to time as prominent Imperial heroes such as Macharius or Ciaphas Caine.
This aside, all the "it's not Emps on the Golden Throne" theories are great.