Whisper of Doom

You whisper an ancient curse of dire potency against your enemies.
Three targets within 15 feet of you must make a Constitution saving throw.
The target takes 6d8+spell casting modifier radiant (if you are good or neutral) or necrotic (if you are evil) damage on a failed save or half as much on a successful one.
On a failed save, the target takes an extra 15 (2d10) damage of the same type and has disadvantage on their next attack roll. They keep taking the damage until they succeed on another Constitution saving throw.

At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, you can target another creature for each slot level above 6th.