Unnatural Signet

From your pointing finger to a single creature you see within range you cause an eruption of chaotic energy bursts over their head. If that creature is maintaining or affected by a concentration effect, each creature in a 15-foot-radius sphere centered on the target must make a Wisdom saving throw. Targets in the area take 6d8 psychic damage on a failed save, or half as much on a successful one.

However, should Unnatural Signet's initial target not be maintaining or be unaffected by a concentration effect, then only that target makes the Wisdom saving throw, and only it takes 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.