Baleful Polymorph

This spell transforms a creature that you can see within range into a new form. An unwilling creature must make a Wisdom saving throw to avoid the effect. If the new form would prove fatal to the creature (for example, if you transform a land-bound target into a fish, or an airborne target into a toad), the subject gets advantage on the save. The spell has no effect on a shape changer or a creature with 0 hit points.

The transformation lasts for the duration, or until the target drops to 0 hit points or dies. If you concentrate on this spell for the full duration, the spell lasts until it is dispelled. The new form can be any beast whose challenge rating is equal to or less than 1/4. The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality.

The target assumes the hit points of its new form. When it reverts to its normal form without dropping to 0 hit points, the creature returns to the number of hit points it had before it transformed. If it reverts as a result of dropping to 0 hit points, then it must make a Constitution saving throw, or it does not regain any hit points and is knocked unconscious making death saving throws as normal. If it makes the save any excess damage carries over to its normal form, and as long as the excess damage doesn't reduce the creature's normal form to 0 hit points, it isn't knocked unconscious.

The creature is limited in the actions it can perform by the nature of its new form, and it can’t speak, cast spells, or take any other action that requires hands or speech, unless its new form is capable of such actions.

The target's gear drops at its feet. The creature can't activate, use, wield, or otherwise benefit from any of its equipment.

If the creature is unwilling, the GM rolls a d100 and consults the following table to determine what form the creature takes, or the GM chooses a form.