TomeNET

(5.16) Experience-draining items                                                
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Some items, such as randart rings of power (dropped by Nazgul) drain your
experience points permanently. Here are some details about that process:
-Experience drain from multiple items stacks, although it doesnt add in a
 linear way. So, wearing two rings of power won't drain twice as fast as one,
 but about 1,5x as fast.
-Experience drain is not temporary, so it cannot be restored by potions of
 restore life levels. To make up for it, you'll have to kill monsters..faster.
-Experience drain won't go further than the experience you need at least to
 maintain your current character level. If you reach that experience border,
 experience drain will stop, even if you still have the items equipped.
 So you will not lose levels from experience drain.
 HOWEVER: If a monster or other effect drains your experience below your
 current level, the experience drain from items will kick in again!
-Experience drain will happen much slower if you're on the world surface,
 ie not inside a dungeon or tower.
-Experience drain will completely hold while you're in a town, so you can just
 take any time you want for shopping or sitting out blacklists, without losing
 any experience at all.