Crystalline Rose

You summon a crystal rose, in an unoccupied space that you can see within range, As part of casting this spell, and on subsequent turns as a bonus action, you can cause the rose to drain the life of surrounding creatures, Each creature in a 20-foot-radius centered on the rose must succeed on a Constitution saving throw or take 2d6 necrotic damage.

When you stop concentrating on the spell, the rose explodes. Each creature in the radius must succeed on a Dexterity Saving throw or take an amount of piercing damage equal to the total number of necrotic damage the rose dealt (to a maximum of 10d6), or half as much damage on a success.