[2021] Was the line about seeing visions of a castle made of steel a potential teaser for an another zombies map. These lines can't be said for no reason

The fun thing about the story elements of Undead Siege in CODM is that it is kind of a central place for all things Call of Duty. The whole game is based around this idea that it can pull from the best and greatest of COD but isn't tied to any specific series or storylines. With Undead Siege it is the same where it isn't meant to continue any other particular ZOMBIES storyline, but can instead be it owns kind of separate space that lightly connects to the rest of the world of COD.