Abyssal Beam

summon a powerful beam of abyssal energy,  everything in the path of this beam (80 ft. line ) must make a constitution saving throw against your spellcasting ability score + modifier, taking 4d10+* necrotic damage on a failed save or half as much (round up) on a successful one.

this spell deals an extra d10 damage at level 15

*5+your spellcasting modifier