Fenrir is primarily a summon, even though other wolf creatures retain that name in other incarnations. Its attacks vary greatly from game to game. In FF6, Moon Song creates Images of the party. In FF9, it calls forth what looks like a giant owl statue to cause earth-based damage to the enemy, and the Maiden Prayer accessory can cause Fenrir's attack to change and do wind-based damage instead.
-Fenrir (NA) / Wolf Devil (JP)
ATK: Moon Song
ATK: Howling Moon
ATK: Terrestrial Rage, Millennial Decay
ATK: Moonlit Charge, Crescent Fang, Lunar Cry, Lunar Roar, Ecliptic Growl, Ecliptic Howl, Eclipse Bite, Howling Moon (Astral Flow)
Not really resembling the wolf Fenrir in the least; it's more meant to be Byak-ko, the White Tiger, of the four Chinese God-Beasts.
CP: Being a Giant in the Form of a great white Cat, revered as a Guardian Spirit high in the snowy Crags of the Mountains far to the West. Its sharp silvery Stare robs those who face it of their Will to Fight, and its vicious Claws rip through Flesh with Ease. It is called the White Tiger for its striped body, and worshipped as an Anima of the Sun.