Diminishing Missile

A bright streak flashes from you to a creature you choose within range and then blossoms with an agonizing scream into a necrotic, blue explosion. Each creature within a 5-foot radius centered on the initial target makes a Constitution saving throw, reducing Armor Class and Attack rolls by 1, additionally taking 4d12 Necrotic damage on a failed save or half as much damage and no change to Armor class and Attack rolls on a successful one.

Targets that fail must continue making Constitution saving throws at the end of their turn or keep the conditions listed above.

Using a Higher-Level Spell Slot. Armor Class and Attack rolls are further reduced by one for each spell slot level above 4.