Drain Life (Remnant)

You consume  a large portion of your vitality, using this vitality you drain the essence of another creature. As you cast the spell, you must expend a number of hit points. The creature must make a Constitution saving throw. The creature takes 12d12 + the hemomancy cost as necrotic damage on a failed save, or half damage on a successful one. 

Additionally, you absorb into yourself the stolen life energy,  for the next 8 hours, the target of this spell has its max hp reduced by half the damage dealt by the dice and hemomancy cost, additionally you gain max hp (but not current hp) equal to half the damage dealt by the dice and hemomancy cost.