I talked to Dave from Nerdarchy and he said they’re using my suggested Insanity Rules (linked below) with just one small tweak. Instead of rolling an attack against the wielder’s sanity score, they have this crazy powerful attribute called “Aether” they can use to power up other rolls to get Advantage. When it’s invoked, the roll is used both as an invocation of whatever attack or boon, and also as an attack against their Sanity defense. So the more successful their attempt at channeling Aether is, the more power they draw upon and the more they cause their own sanity to slip away… Personally, I love it! 
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