Grand Nuage

The Grand Nuage (グラン・ニュアージュ), commonly called Guardian Base (ガーディアン・ベース), is the headquarters of the Guardians in the Mega Man ZX series, an airship.

Mega Man ZX
The Guardian Base is Area X, which can only be reached with a Transerver after complenting the first three missions. It is attacked by Slither Inc. after the defeat of four Pseudoroids, and the player must fight against several Galleons and Prometheus.

Most O Disks are located in Area X, and the player can obtain a E Tank with Cédre and a W Tank by hitting the doll in Prairie's room several times. Aile can also change the color scheme of her clothing by speaking to one of the Guardian members. The soundtrack for this area is called Sky High - Grand Nuage.

Mega Man ZX Advent
The Guardian Base has a short appearance, where it is used to reach Ouroboros.

Other media
The Guardian Base appeared in the Mega Man ZX manga.

Trivia

 * Grand Nuage means "Great Cloud" in French.
 * The Guardian Base is possibly powered by the Ciel System, as when the player go to the engine room, its power source is similar to what Ciel is holding (in her artwork).
 * Prairie's room on the Grand Nuage is full of plush, Cyber-Elf dolls, which is a large cameo to the Mega Man Zero series. One of these dolls, the witch-type Cyber-Elf from the first Zero game, can be cut down from the ceiling and repeatedly attacked. Doing so will eventually merit the dropping of a Weapon Tank.
 * Additionally, plush dolls of the Pseudoroids will begin to decorate the room if the player manages to defeat the corresponding bosses without inflicting damage to their weak spots where the Biometal fragments are stored.