Ralsei might be able to go to the festival, because I have a theory that he isn't fully a Darkner, but a mix of Lightner and Darkner, or as I like to call it... a Greyer/Grayer!

1. Ralsei knows about the UI, because in the tutorial he tells you how to time your FIGHT bars, but HOW could a darkner EVER possibly know that?! It’s simple…. BECAUSE HE ISN’T A DARKNER!!!!

2. Ralsei can travel in between Dark Worlds that should be VERY far away from Castle Town. How does he do it? Simple… HE GOES TO THE LIGHT WORLD!!!! That MUSSSSSST be how he ALWAYS just so happens to appear JUST behind Susie and Kris!!!!!

3. He looks just like a Boss Monster, and Boss Monsters are most DEFINITELY Lightners!!! The only Boss Monsters we see, atleast in DELTARUNE, are Asgore and Toriel, and they are both Lightners!!!

4. Ralsei says he is a Prince of Darkness, but he stands in front of a fountain of Pure Darkness. Every other Darkner is "born" from a specific fountain made of a mix of things (toys, computers, cards, etc.). If Ralsei is "Pure," he might be the original type of Darkner… A BRIDGE BETWEEN THE LIGHT AND DARK WORLD!!!!!

so what im trying to say is... ralsei could come to the festival if this is true

(btw this IS a serious theory)