system
Given the following post, respond as if you're commenting on Reddit:
human
[Overlord] How does sacrificing XP work?

I don't think I've ever seen an RPG style game where you need to sacrifice XP, or at least not in the way Overlord does it. Wouldn't bringing yourself down a level or something cause problems like suddenly being unable to use some of your equipment or abilities?

Also, how does Ainz increase his XP in the fantasy world compared to Yggrdasil?
gpt
Dungeons and Dragons 3.5 has XP costs for a lot of spells, though Pathfinder got rid of it and it didn't appear in later editions. Just make sure to have equipment that works at a lower level if you're going to be throwing around spells with XP costs.