He watched the zombies advance with care, idly worried that they seemed to be intelligent again, and mentally made a note to identify any casters, if possible. Instead, he placed himself up on top of the wall, and began picking off the more dangerous looking zombies as they advanced. After they started compressing up, though they took a bit to ensure no casters were present with fireball first, he pulled out one of his secret weapons, an shell of rock, carefully pitted and notched though no one local would recognize why, and pressed the two halves together. This compressed the fire element of the magic grenade, and he flung the two pound weight into the zombies, before yelling for everyone on the wall to duck. His warning was a second early, as there had been no way to set an accurate timer on the thing, but the resulting explosion SOUNDED right, and he popped back up to both survey the damage and to continue picking off heads.