Cornered Fang

Deal 1d12 piercing damage to one enemy. When you hit an enemy that is weak to piercing for the first time this turn, take one more action this turn. On a 14-20, deal double damage and act as if you hit a weakness. Does not work on enemies that nullify piercing. Costs 10% hp. If your initiative is lower than all enemies initiative, this spell deals double damage.

(This is for a homebrew persona campaign I'm making. More Personas and spells will be made as time goes on. A feat has already been made called the "Persona User (Wild Card). If anyone has any tips, feel free to provide them)