Forced Donation
At 11th level, you gain the ability to drain from a short distance. You can rip blood from an enemy with blood (as ruled by the DM) and siphon it into your own pool. At a range of 20 or lower, make a ranged spell attack with Constitution as your modifier. On a successful hit, the enemy takes 2d10 necrotic damage. This damage becomes 3d10 at level 15 and 4d10 at level 18.