I just watched Dr strange and i have a theory. Cassie said that in TWP, we will see characters from different generations unite and face the biggest threat ever. First i thought this meant that characters from TID or TLH will come back as ghosts or astral projection or some other magic but now i am thinking that maybe they will be brought back from a different universe or timeline.
Thule is an alternate dimension and the the time there is after the timeline that the non thule characters (the timeline we are seeing in the books) are living in. Livia was older then the non thule Livia and if she appears in TWP she's gonna be around 20. I think Dru is still alive in thule bc livvy said that Dru left and never returned. We also have to remember that Thule Kit is still alive. Maybe the alternate dimensions of kit and dru will be evil. Though they will be a little older then the non thule kit and dru but i dont think that will matter much.
Anyways, what im tryna say lmao is that the twp characters (aside from the mains) will be from thule and other universes where the timeline is different then the current timeline, i.e the timeline in the other universe is gonna late 1800s/ early 1900s where the TID gang is still alive.