Polymorph

Turns the mob you aim at into a chicken, permanently. The chicken drops the original mob's loot instead of its own when it dies, which is what makes it a farming tool rather than a delete button. Only the mob's type is remembered, so its gear and name are lost.

The level caps how tough a target can be, measured on max health: 20 at I, 40 at II, and so on up to 300 at level IX. At level X there is no cap. A mob over the cap is left as it is.

Cast at a player, it instead surrounds them with a flock of ten jealous chickens that hunt them for a minute, tougher at higher levels. Each caster can have only one flock alive at a time; a second cast at a player while it lives is refused. Costs soul.