The Iguions begin the battle with Reflect due to Carbuncle's influence. Resonance is a magic attack used only when the two Iguions are present. Magma Breath is a Fire-elemental attack that can petrify a target. Iguions are immune to the Fire element. They are weak to Earth.
The player should draw the Guardian Force from the Iguions, thus taking their Reflect away and gaining Carbuncle. Afterward the Iguions are easy to defeat with GFs, as long as the player doesn't summonIfrit. Brothers is a good choice of summon because they deal Earth damage, which the Iguions are weak against. It may be better to concentrate on one Iguion at the time, and use Limit Breaks when they become available.
Iguion comes from "iguana." [view·edit·purge]Iguana is a genus of herbivorous lizards native to tropical areas of Mexico, Central America, several islands in Polynesia and the Caribbean. Two species are included: the green iguana widespread throughout its range and a popular pet, and the Lesser Antillean iguana native to the Lesser Antilles and endangered due to habitat destruction. The word "iguana" is derived from the original Taino name for the species, iwana.