Midgardsormr

Midgardsormr (ミドガルズオルム Midogaruzuorumu), also known as Terrato or Midgar Swarm, is a recurring summon in the Final Fantasy series.

Final Fantasy VI
Midgardsormr, is an Esper obtained in the Narshe mines in Yeti's Cave. Once finding it, a fight will ensue with Umaro. If Mog is in the party, he will convince Umaro to join the party, after which both Midgardsormr and Umaro are obtained. Midgardsormr's summon spell, Abyssal Maw (Earth Aura in the original SNES version), deals earth-Elemental damage to all opponents. Its Spell Power is 93, and it is unblockable. However, it cannot hit flying targets. It costs 40 MP to summon, and it teaches the following spells:
 * Quake X3
 * Graviga X1
 * Tornado X1
 * At Level Up: HP +30%

Final Fantasy Tactics
Midgardsormr, called Midgar Swarm in the PlayStation version, is a summon spell used by Elidibus.

Etymology
Midgardsormr is the Old Norse word for "Midgard Serpent", the World Serpent. The word 'Midgard' comes from Nordic legend as the home of humans, and the Midgardsormr will kill Thor during Ragnarok.

"Terrato" may be related to the Italian word sotterrato, which means "buried".