The steel balls that the human mages dropped down didn't explode, rather, they released thick and hot water steam, and with 7 of them being released close to each other, Matthew's vision was obstructed and he could feel the heat from the air that he was breathing.
It was as if he was put into a very hot, steamy sauna.
He heaved a sigh as he realized that the steel balls weren't grenades, but he didn't spend too much time idling as he activated his heat sense, trying to find the running mages, but due to the hot steam that the steel balls released, Matthew could only find his vision turning all red without seeing any silhouette of a human.