Cloud Vortex (クラウドヴォーテックス, kuraudovōtekkusu) is a Phantasma mentioned in gaiden story Practical War Game and High Card All Raise. As his name implies, it's existence is akin to a sentient cloud, a manifestation of natural disaster.
As the Elves collaborated with the Fairies to develop a rite capable of controlling high level Ixseed, Cloud Vortex became test subject. However, the rite failed and Cloud Vortex went berserk. As a result, the Flügels intervened and destroyed all facilities and personnel involved in the development, while Cloud Vortex himself was slain by a squadron of 30 Flugels led by Jibril.
Despite the great loss, the data gathered during the experiment was put into good use by the Elves and eventually led to the capture of Insein Nebia. However, the destruction of facilities and exposure of the Fairies' homeland also resulted in the Elves having to split their troops for defense, leaving the capital Melriune exposed. This led to the invasion led by Lóni Drauvnir and eventual destruction of the capital in the hand of Jibril.