Drevet' Shadow Maw

When you cast this spell a ball of shadow releases from your palm and explodes into a void of shadow and teeth in a 20ft radius. It is considered difficult terrain, if a creature ends its turn in the affected area it must make a constitution saving throw. On a failed save the creature takes 4d8 necrotic damage and 4d8 piercing damage, half on a success. If a creature fails the saving throw by 5 or more the caster heals for half the damage. If the creature succeeds by 5 or more the caster takes half the damage. If there are 4 or more creatures in the affected area increase each damage type by 2d8. If there are 8 or more increase each damage type by 4d8. If there are 12 or more increase each damage type by 6d8.