Casting this curse requires an empty hand, and something of the target’s, be it a possession, their blood, or their hair.

You create a small doll which is an effigy of the target in your hand.
The effigy has half the target’s HP, and when its HP is depleted it is destroyed.
The effigy is linked to the target, and damaging the effigy damages the target.
The target’s absorptions, immunities, resistances, and damage reductions apply to damage taken from the effigy.
The target may use abilities which can be used in response to taking damage from a spell on damage taken from the effigy.
Casting a curse on the effigy redirects that curse to the target.

Damage from the effigy cannot reduce the target below half HP.
The effigy does not take fall damage.
Only one effigy of a target may exist at the same time. When a new effigy is created, any prior effigies stop being magical.