In the Geno run, Chara said that is was Frisks determination that woke them up from Death. So it was safe for me to assumed that this was just some BS a determined soul can do. But then I remembered what the book said about human souls. This got me thinking; What if Soul Fusion & Soul absorption are two separate things in the UT universe. Soul absorption would involve taking a soul and gaining its power becoming a more powerful being. Soul fusion could just be the merging of two or more souls into one, making them share a body while not giving them any extra power. . . Other than an increase in Determination. Maybe even enough to obtain a save file.

If it works for humans, then could the same thing work for monsters? I don't think so, at least not traditionally. I believe with enough DT a soul (Monster or Human) can merge with another soul. But due to most monsters not having DT, this isn't something normally possible unless the monster has a high amount of DT. Just look at the amalgamates for example. The got pumped with so much DT, they started to melt & merge together. And that was just their bodies. We don't even get too see there souls!

Thanks for listening to my little theory post. Hope you have a good day/night/afternoon wherever you are!