Snuff Out comes out and Vendetta stays in the sideboard: both can only destroy nonblack creatures, and Psychatog is black as well as blue, so neither can target it. Since Psychatog is their only real threat, a card that can't hit it is dead here. Diabolic Edict replaces it because Psychatog is frequently their only creature, so forcing a sacrifice works regardless of its size or color, and as an instant it can be cast in response to pump activations or at the end of their turn. Smother stays in, as Psychatog has mana value 3. Ravenous Rats stays in, since it still strips a card from a hand full of Counterspell and Gush alongside Duress and Cabal Therapy. Keep Withered Wretch in since exiling their graveyard denies Psychatog's exile-based pump and shrinks the count for Circular Logic.