Volatile Carapace

As a responce to taking damage from a source other than Psychic or Force, you sprout spikes in a 30ft square centered on yourself, each target you choose within the square must roll a Strength Saving throw or take 2d12 piercing damage on a fail, or half as much on a successful one. Afterward, the spaces inside the square are treated as difficult terrain.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d12 for each slot level above 2nd.