During the first phase Gemesaur King advances slowly using its giant body to try to enclose Link in a narrow spot while also using its tail to shoot jeweled projectiles. This attack is easily noticed for the Gemesaur King twirls his tail; this attack can also be blocked by the shield. During this time the best way to inflict damage to the Gemesaur King is by placing Bombs and throwing them at his body; doing so causes several Rupees to fall. As he takes bombs his body loses crystals from where it was hit, and his entire body, including his mask, must be blasted before the second phase begins.
At the second phase, the Gemesaur King unleashes a massive beastly roar that extinguishes the torches, making the battleground dark and himself surrounded by a dark aura. During this time the Gemesaur King will violently assault Link with his massive body at tremendous speeds, which is almost if not outright impossible to avoid through conventional means. The only way for Link to succeed is to merge with the walls and wait for when the Gemesaur King is away to then light the torches and cause his dark aura to banish. Once this is done Link can damage the Gemesaur King but the monster will move faster and enclose Link much more aggressively than before, and will eventually turn the lights off once more, at which point the tactic must be repeated before the monster falls.