So I've already seen new theories about who Bone Guy is since Hope said she felt like she's fought him before.
Theory 1: that Bone Guy is Clarke because him and Hope fought back in season 2. I don't know if I would call what happened between them a fight. She just pushed him away before he could use trident on her and the blasted him with a ball a light when he went into simu-Landon. So like I said I don't know if I would call that a fight.
Theory 2: that Bone Guy is still somehow a part of Landon and it feels like Hope fought him before she fought simu-landon in season 2. I don't remember Hope ever fighting simu-landon before. But I guess it could still be possible that it's still somehow part Landon and it feels familiar to Hope because she's around Landon a lot.
Theory 3: that it's somehow dark Josie and Hope did fight her at the end of season 2. That would be an interesting twist if it was Dark Josie. Like maybe somehow when Lizzie gave the necromancer the dark magic that was in Josie that somehow the dark part of herself went with it. But who knows.