Hashi was nearby. He was about to land another sneak attack when Tiemezzys was occupied but Jack beat him to it. He was now staring at Jack in disbelief. His mana sense also couldn't detect Jack. This level of mana concealment was what made him believe he was the best assassin in the world. He found it hard to believe there was another person who had the same expertise as him.
Jack's mana concealment had undergone a huge upgrade due to his practice using the Chalice of Blood. By learning how to camouflage his mana to infiltrate the artifact, he also learned how to mask his mana to make it appear as if common mana in the air. This practically made him invisible to mana sense.
Even though Jack managed to land the powerful hit, he had brought himself too close. He was Tiemezzys' primary target. Tiemezzys ignored everything else and lunged at Jack.