But here's my real theory on what Ralsei is! Ralsei... is an AI chatbot.
Think about it. What would Kris bring with him almost everywhere? His phone!
If you've ever talked to a chatbot, you'd know that they are incredible at being pushovers.
One time, (mentioned in Chapter 2 iirc) Alphys recalls Kris chatting with Asriel all night once upon a time. It could be possible that Kris made a chatbot of Asriel, because the real Asriel is never available.
I think I recall that AIs can be used for RPG Game Masters.
Okay, I'm out of instantly recallable points towards my argument.
Although... Now that I think about it...
The internet's been out for the entire series. AI Chatbots need the internet to be accessed... But mobile data exists, so it's still possible.
Ralsei has never been seen when we enter a dark world, or exit. He's always been offscreen. So maybe he actually is Asriel, popping into the dark worlds and leaving to the light world in secret???
