Enervating touch

You create a ghostly, skeletal hand in the space of a creature within range. Make a ranged spell attack against the creature to assail it with the mind numbing  chill of the grave. On a hit, the target takes 1d4 necrotic damage, and must make a concentration check to cast or maintain a spell until the start of your next turn. The DC of the check is 10 plus the damage caused. 

If you hit an undead target, it also has disadvantage on attack rolls against you until the end of your next turn.

This spell's damage increases by 1d4 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).