Although internal organs had little to no importance for the functioning of any undead, they were still most definitely linked to their HP just how it was with any other creature - the only difference for the undead was that although destroying a particular organ would decrease their health points, it would not immediately incapacitate those beasts in any significant way as it would do to the living.
Internal organs were the first weak point that a necromancer would get rid of in their summoned monsters as destroying them one by one with enough time in between for the creature HP's regeneration to cover the loss would not bring any disadvantage in the long run.
"You can go to the other side with ease, I will be personally sending your master there, following after you...!"
Durian laughed, unveiling his plan to make the defeated enemy even more miserable - although in all honesty - he was unsure whether the monster could hear him properly.