Touch of Hadar

Your hands or fingers become twisting, purple tentacles. When you cast this spell, you make a melee spell attack against one creature within 5 feet of you. On a hit, the target takes 1d8 necrotic damage, and until the start of your next turn you can repeat the attack against the target as a reaction instead of making a weapon attack if it provokes an opportunity attack from you. Your limbs or digits return to normal at the start of your next turn.

At Higher Levels. The spell's damage increases by 108 when you reach 5th level (208) 11th level (3d8) and 17th level (4d8)