Cros's Blood Draw

You draw your finger across an area of skin on a creature, and they take 1d4 slashing damage.. The skin cuts, and starts expelling blood (10u / Turn). When the creature regains hit points, no matter the amount of healing, the blood loss reduces by 1u / Turn. At the end of every turn, the bleeding creature takes 1d6 Necrotic Damage, and for every 5ft they move, they lose 1u of Blood and take 1 Necrotic Damage. When they use the body part that is injured, they lose 3u of blood and take 2 Necrotic Damage. They gain an exhaustion point when lose the corresponding amount of blood to your body size:

Tiny: 10u
Small: 25u
Medium: 30u
Large: 50u
Huge: 100u
Gargantuan: 150u

A creature that has gained 2 exhaustion points this way is knocked prone, when they gain 3, their speed is reduced by half, when they gain 4, they become incapacitated, and when they gain 5, they are knocked unconsious. 

For every level you upcast this spell, they lose an additional 5u of blood per turn.