Armogohma appears as a large spider, resembling a Gohma, that has eight legs and a huge eye placed right on its back. It is very hairy, this can be seen anytime it is close enough to Link. It was corrupted by the Mirror Shard and turned into a giant spider. It is possible for it to have simply been a Baby Gohma that when touched by the Mirror Shard turned into that.
The fight against Armogohma has two phases.
The first phase of the battle involves Armogohma walking around on the roof, usually with its weakspot, its eye, closed. However, after a while it will stop and aim a Fire Laser that. Comes out of its eye at Link. Now is the time to attack , as Link must hit the eye with his Hero's Bow. Armogohma will screech in pain, and fall to the ground. Now Link can use his Dominion Rod on one of the Ancient Statues in the area to attack Armogohma's belly. After two hits, the spider will get up and the battle will continue. However, Armogohma will change its strategy. It will first drop down loads of Baby Gohma, mainly to distract Link. He must kill them all and turn repeat the Bow-Dominion Rod attack. After 4 more hits with the Ancient Statue, Armogohma will appear to fall.
The second phase of the battle is quite pathetic, as it simply requires Link to hit the eye of Armogohma, which is now walking around on the floor surrounded by Baby Gohma, with his Hero's Bow a few times. It is rather simple.