There was a group with enough money and influence to stay out of legal trouble, and they were experimenting with a way to weaponize disembodied souls via the power of an evil monster. The latest experiment was with a PAYDAY 2 game disc infused with said power. Unfortunately, there was an accident and the disc got out into the world. Five college students found it and started playing it- and it killed them. Horribly. And trapped their souls inside. The five figured out that they were effectively omnipotent in the game world and chose character data to fuse with so they could take form in it. Their presence corrupts their vesselsβ appearance a bit.
Erin chose Dallas. She says it was because she's the leader of the group and their shoulder to cry on, but she really just did it so she would get to hear the medic bag line as many times as she wanted.
Vera chose Wolf because she's Swedish too and he was her favorite anyway.
Elijah chose Hoxton because he liked the accent; he's also the one who uses his power over the game most.
Travis chose Chains because that was his main anyway.
Mia chose Houston because she liked his character and enjoyed teasing Elijah.
And another ghost, Mick, who worked on the project, was sealed inside when the disc got out in the real world (also met a horrific end), and he chose Jacket as a vessel because they thought it would be easiest to hide in.
At present, they hide from the monster while trying to find a way out/make their afterlife not suck. There have been... mixed results.