The new core doesn't offer a lot of skills for Silas, and this might be one of the more dangerous. Every time you apply it, you're risking 20% of your sanity. Then again, with the limited weapon pool, this is an excellent partner to meat cleaver. Take a risk on another check and then calm yourself with a crowd-pleasing ghoul decapitation. What Mystics like, especially when the Jim Culver ally's in play, is you can commit this for others and gain the "benefit" yourself. Agnes's ability is gated to once per phase, but this is a perfect way to deal damage to a foe in Mythos. And it's even a spell, which means Arcane initiate can fetch this for you.