At some point today, Cabin 7 (Tony Stark (AA), Peggy Carter, Marco Bodt, Rogue (616), M'Baku, Tony Stark (616), Sarah Williams) will notice that Steve Rogers is missing. Cabin 7 no longer has the use of their map.
Cabin 3 (Bruce Banner (MCU), Harry Potter, Bruce Wayne (DCEU), Jasper Sitwell, Obi-Wan Kenobi, Leia Organa) will notice that Bones McCoy is missing.
Cabin 4 (Sirius Black, Riri Williams, Logan, Bruce Banner (616), Groot, Kamala Khan) will notice that Regina Mills is missing.
The Upside-down
To return to the land of the living, Regina, Leonard McCoy and Steve must Complete a Upside-Down prompt.
This can be done through communications with Romeo, a log or a narrative. Those who were taken by monsters will remember their abduction. Those who were killed by their own story prompts will remember how they died.
Remember, there is no network access in the upside down. They can only communicate through a divination post with someone in Romeo.