Articus' Devolutionary Warrior

If your setting has Chronurgy or Chronomancy, this spell is in that school instead of transmutation.

When this spell is cast while touching a humanoid, the evolutionary clock of target is reversed, with its fighting ability increases at the cost of its mind. If the target is unwilling, they must make a Wisdom saving throw. On a failure, the target gains 1d6 in Strength, Dexterity, and Constitution (to a maximum of 20), while losing 2d6 in Intelligence, Wisdom, and Charisma (to a minimum of 1).

The target has a marked increase in body hair, and other physical changes might be noticed (such as longer arms or a hunched posture). The target's nails and teeth become sharper and usable as natural weapons (of which the target has proficiency). These weapons deal 1d8 slashing or piercing damage, and use the target's Strength modifier. If the target already had natural weapons before the spell was cast on them, they are increased to deal 1d8 damage and also get a bonus of +1 to attack and damage rolls. At any Intelligence below 3, the creature shuns weapons for their natural weapons.

For an unknown reason, Articus' Devolutionary Warrior does not work on elves. Most believe elves were created whole without evolution, rather than with an innate resistance. Half-elves gain 1d3 in Strength, Dexterity, and Constitution and lose only 1d6 in Wisdom, Intelligence, and Charisma, but are otherwise subjected to all other effects of the spell as normal. The spell will also not work on any construct-based lifeforms (such as Warforged) or other races created without evolution.