How to reduce sanity as a Warlock?

Hey there. New player here, on my third run or so of CoE5, and im playing warlock. i'm doing good, expanding fine, with one tiny issue. my main commander is a great warlock of air, and i had him up in the elemental plane of air to explore and get more diamonds. Well there I accidentally slipped into the void (i assumed it was like the sky, and i could fly there as long as i didnt get exhausted). I was in there for quite a few turns and my main commander is now in Celestia with 51 insanity. He's basicaly immobile, and with how important rituals are for warlocks (even if i could get another commander up to celestia) I kinda need him to not be insane. Any magic items or spells I can look for?