Tempest Cloak

You call forth the powers of a mighty tempest to protect you. For the duration, the space within 15ft of you is charged with surging storm energy, feint rolling thunder, and light rain.

When you cast this spell, you can designate any number of creatures you can see to be unaffected by it. An affected creature's speed is halved in the area, and when the creature enters the area for the first time on a turn or starts its turn there, it must make a Strength saving throw. On a failed save, the creature takes 3d8 Lightning or Thunder damage (your choice). On a successful save, the creature takes half as much damage.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.