It's more to do with their souls than the snails. They aren't as powerful as humans, so it's just temporary and they won't stay for too long, but their souls stay around after death.

There are a few of us in each region that are stronger than the others. At least one of the skeletons in the eastern caverns has potential, and there are a lot of members of the Royal Guard in that area. Undyne is in Waterfall - she's the captain of the guard that I mentioned, she'd love you. And where I work...well, there's me, of course. And my creator is pretty good with magic and technology, but she doesn't fight.

We're all pretty powerful, but we've got nothing on boss monsters.