Quote Originally Posted by Emanick View Post
I've never played at a high enough level in 3.5 that it was an issue, so I was going off what somebody else had told me about the relevant rule. I've just double-checked and you're right, the rule does seem to be that you can't spend enough XP on item creation to lose a level. I apologize for the misinformation

That means that, in order to craft a Ring of Universal Energy Immunity, you would either need to be level 87 in order to spend 86,400 XP to craft it without dropping, or you would need to have a DM who permitted you to spend the XP in increments over the six or so years it took to make the item (or seven months, if you have the Efficient Item Creation epic feat). I think the XP-incrementing option is sort of reasonable, but since in my opinion the item shouldn't even exist, if I was DMing I probably still wouldn't allow it.

Still, if you consider the latter interpretation a possibility in-universe, I guess it's still possible that Xykon made himself one.
It's mentioned that you can postpone leveling up even when you have enough XP for it, specifically for the purposes of spending XP on stuff.