Ralsei is a shadow (I’m working off of @chiya-eltanin’s theory, I personally find it the most persuasive explanation of what Ralsei might be), but isn’t just Kris’ shadow, because if he were then it makes no sense why Susie/Noelle/Berdly’s shadows aren’t also darkners. Instead, he’s specifically the shadow of the host of the Soul - the shadow of the person illuminated by the Soul’s light, distinct from shadows made by mundane sources of light.
The incorporation of (a lack of) ‘divine’/outerworldly light in his existence means he isn’t merely a shadow of what that host looks like, but reflects what they wished they looked like - the shadow they wished they had. Kris-having-the-Soul’s version of Ralsei looks like the other Dreemurrs because Kris wants to look like the rest of their family. If Susie had the soul (and maybe this is true during the scenes we’re sent to her, it’s not like we see him then and it would be a pretty obvious indicator of where we are and whether he’s safe to speak to Kris privately, meaning he knows exactly when we come back and to stop talking) then he’d probably look a lot like her dark world self or like ‘Susiezilla’, since she’s said that she prefers those forms over how she looks in the light world.
This obviously doesn’t have… basically any real supporting evidence, but damn if it doesn’t make emotional sense to me. The shadow-Ralsei theory has rung truer to me than him being some specific object since I read chiya-eltanin’s post, but the fact that there’s only him and not any darkners who could be Susie, Noelle or Berdly’s shadows bugged me - the prophecy specifying only one lonely Prince of the Dark wouldn’t necessarily preclude there being other people’s-shadow-based darkners, but if Ralsei is defined by being a shadow from that particular light source then his uniqueness makes a lot more sense.
This theory also makes Susie’s resolve to never let him be left behind or forgotten a lot more tragic. Even if we’re not the Angel being banished, the game won’t go on indefinitely. If we leave, and our Soul, our avatar in the game world, disappears with us… What happens to Ralsei?
