Peter feels like the odd man out, the one that has no clue what's going on, but he's also the only one who's memories of Dawn aren't degrading. He's the one most qualified for sitting with Dawn on the couch and keeping her rooted here. Any solid form she had that he could hold onto has disappeared. Right now, he's sitting on the couch next to Dawn, his knees to his chest, arms wrapped around them as he talks to her about the things they've found in the hotel, the things they're still going to find, trying to give her a purpose and reason to hang on a little while longer.
Spell doing + Dawn sitting