Cube

This spell transforms a creature that you can see within range into a cube. An unwilling creature must make a Wisdom saving throw to avoid the effect. 

The transformation lasts for the duration, or until the target drops to 0 hit points or dies. The target's game statistics, including mental ability scores, are replaced by the statistics of the cube. It retains its

A cube is an unaligned construct with no movement speed, 1 (-5) in all stats, no proficiencies, 6 hit points, AC 6, and is challenge rating 0. The cube cannot take actions, speak, cast spells, or take any other action that requires hands or speech.

The target takes on the hit points of a cube. When it reverts to its normal form, 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, any excess damage carries over to its normal form.