User blog comment:Endless Exceptions/Custom New Item Ideas: Necklaces./@comment-5571637-20121010223959/@comment-3475363-20121011104659

"Everytime you do a skill there is a chance (30%) that the ability you used only cost half. BUT everytime you do a skill there's a 3 second cooldown on your item. So you can spam as much as you want but only ONE SKILL in those 3 seconds has a 30% chance to cost half the mana.

So most of the time, you won't even get the "refund"."