The Heart Grasp Spell was a curse-type spell designed to strike directly at the heart of the target.
With all four casting the spell simultaneously, they were all confident that Vale didn't have countermeasures as he had yet to consume his third Darkness Possession potion.
Furthermore, they already knew about the Malefic Branch Spells, the Spell Dispersion and the Incorruptible Body. According to the information they received, Vale's achievement with these spells shouldn't have reached the Intermediate Realm yet.
With that in consideration, Vale would be incapable of resisting four curse spells simultaneously.
The blond man was also confident that Vale would die at this point since he should be vulnerable to this attack.
The curses hit Vale at the same time, and they heard two cracking sounds. It seemed that the spells shattered his defenses as well.