For the first phase of the battle, Grinexx will swim around the lava beneath the platform. It will occasionaly shoot a blast of fire through the platform. Link must drop an ice cube using the Ice Rod through a hole in the platform onto Grinexx. Repeating this process will cause the second phase of the battle to begin.
Grinexx will now slowly walk around the platform and snap at Link. It also will retreat into its shell and perform one of two attacks; it will either retreat into its shell and ricochet off the walls around the room in an attempt to crush him, or it will create a blast of flames around itself. While it is ricocheting off the walls, Link can avoid taking any damage by going into the corner of the room and holding up his shield toward the center of the room. To defeat Grinexx, Link must either slash its head with his sword or attack it with the Ice Rod until it is destroyed.