Blood Syphon

You attempt to syphon some of a creature's life force from afar. A creature of your choice within range must make a Constitution saving throw. On a failure, it takes 2d10 necrotic damage and has disadvantage on the next attack roll it makes before the end of your next turn. It takes half as much damage and doesn't suffer disadvantage on a success. Creatures that don't have blood have advantage on the save. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d10 for each slot above 1st level.