http://www.newsweek.com/black-ops-4-blood-dead-easter-egg-ending-explained-richtofen-die-1180050

Call of Duty: Black Ops 4 players recently uncovered the Blood of the Dead Easter egg, and its ending cutscene prompts more questions than it answers. With a little help from Zombies theorists like FantasticalGamer and JohnyJ25, we’ll fully explain what Richtofen’s fate means for the Aether timeline.

The end cutscene for Blood of the Dead shows us there are two versions of Richtofen from different dimensions. The first Richtofen is our playable character. We’ll call him Primis Richtofen. The second Richtofen wears the Red Cross Uniform seen in Revelations. He was presumably frozen under Blood of the Dead and was freed once Primis Richtofen used his blood to power the Warden’s machine.