Ragnarok (summon)

Ragnarok (ラグナロック Ragunarokku) is a summon who has only appeared in one game in the main series, but has appeared in a spin-off.

Final Fantasy VI
Ragnarok is an Esper, not to be confused with the sword, even though the Magicite can be used to make the sword. It is obtained in the Weapon Shop in Narshe in the World of Ruin. Locke is needed to access the shop. The owner in the back offers to hand over the Magicite or refine it into the sword. If the player chooses the Magicite, its summon, Metamorph (Metamorphose in the Advance Version), transforms an enemy into a random item. Its Hit Rate is dependent upon the target, and it is not affected by the Vanish/Doom bug. It costs 6 MP to summon, and it teaches Ultima at a rate of X1.

Final Fantasy Fables: Chocobo Tales
Ragnarok is one of the five Promo cards. In the Japanese and American versions, he must be downloaded from a download station. In the European version, the player simply has to enter the code A, L, Left, Up, R, R on the Download Pop-Up Card screen.

Etymology
Ragnarok is an event in Norse Mythology that is similar to the Apocalypse. It is an event that is set of by the death of the god Balder, which was orchestrated by Loki. The Ragnarok was a final clash of all the major entities of Norse mythology. This caused all of the human spirits up in Valhalla to come down for the final battle. This bloody encounter ebbs with the destruction of the Universe and Balder along with a little handful of entities that are put in the bodies of children and only contain memories of the world before Ragnarok. Those entities would become mortal.