Dark Inferno

You create a dark orb of flame to hurl at a target. Choose a creature within 60 feet. That creature must make a constitution saving throw or take 6d4 fire damage and 4d8 necrotic damage and have any healing they receive halved for the next 1d4 turns. The target can roll a constitution save at the end of each of these turns to shrug off the effect. Additionally, if the target has any natural regeneration, such as that of a troll, the target does not receive this benefit for that turn. On a success, the target takes half damage and does not receive the reduced healing.

At higher levels: For each spell slot above 4th that you cast this spell, the damage of the fire increases by 1d4 and the damage of the necrotic increases by 1d8