Cloud Sea of Alrest

Cloud Sea of Alrest (, Sea of Clouds in Alrest) is a stage in Super Smash Bros. Ultimate based on Xenoblade Chronicles 2. It is bundled with and  in Challenger Pack 9, which is also part of the Fighters Pass Vol. 2. It was released on March 4th, 2021.

Stage overview
The stage takes place on top of Azurda (also known as Gramps), serving as the home of Rex in Xenoblade Chronicles 2. The stage continuously floats through the skies as other Titans fly by. The entire stage has a gentle sway that slightly changes the altitudes of platforms. There is a single floating platform on the left end of the stage, and Azurda's neck acts as a mild slope on the right side. Occasionally, Gramps will raise and lower his head, which will affect the angle of the slope. He will also turn his head to look at the Titans, which temporarily shrinks the size of the stage. The stage contains indications for when he is about to turn his head, such as his neck shaking, a windmill spinning faster than usual, and the door to Rex's house closing. If there are fighters standing on Azurda's head or hanging from his horn when he turns his head, they will slide inwards rather than fall off. Throughout the battle, Azurda will provide banter and comment on the state of the battle. When the battle starts, Azurda will say "I want to see a good, clean fight. Do you hear?" When a player is down to one stock, Azurda will say "It seems that we will soon have a winner!" Other examples include when a fighter is KO'd, Self-destructs and when a Titan appears in the background. He also possesses unique lines for and  if they are present in the match.

Occasionally, the following Titans will appear in the background:
 * Goldmouth, the Argentum Titan, with the Maelstrom following behind
 * Gormott
 * Uraya
 * Mor Ardain
 * Genbu
 * Indol

The order the Titans appear is randomly selected at the start of the match; once all six have appeared the cycle repeats in the same order. Additionally, the lighting and color scheme of the background changes as the Titans appear.

The following characters appear as cameos in the background, with one Driver and Blade pair being randomly selected: They can appear either in front, to the side or on top of Rex's house, standing either together in one spot or standing apart in two different spots.
 * Nia and Dromarch
 * Tora and Poppi α
 * Mòrag and Brighid
 * Zeke and Pandoria

Ω form and Battlefield form
The main platform of the Ω form and Battlefield form does not feature Azurda as the main platform, but instead uses a haphazardly constructed airship that matches the size of and, respectively. Additionally, the character cameos do not appear; however, the Titans still appear in the background.

Hazards Off
With hazards off, Azurda's head does not move at all, staying at the starting position throughout the match.

Origin


The layout of the stage comes from the beginning of Xenoblade Chronicles 2, where Rex lives on Azurda's Back as they swim across the Cloud Sea in search of salvaging jobs. The Titans spotted in the background are all areas that can be explored in the game. The background characters that appear on the stage are party members that Rex befriends throughout the story's events.

While this stage is a home stage for / and, they can only be present at the beginning of Xenoblade Chronicles 2 during a New Game+, as Rex loses Azurda as a home before encountering Pyra, with Azurda regenerating into a small larval stage for most of the game. Although Azurda regenerates into his adult form at the end of the game, Rex's house on his back no longer exists. Rex's fellow party members cannot be present on Azurda's Titan form at all until the very end of the game, as they do not appear at the start of a New Game+, unlike Pyra/Mythra and other Blades previously unlocked (including Shulk).

Tournament Legality
Cloud Sea of Alrest has been banned from tournaments due to the large slope on Azurda’s neck creating unusual, potentially disruptive geography. The lower blast zone somewhat obscures characters that are inside the cloud sea.

Trivia

 * Sakurai stated that the reason why Azurda is not the main platform for the Ω and Battlefield forms is because the development team thought he would be "crushed into jelly" if they tried to make him fit the shape and size of Battlefield.
 * During one of Pandoria's animations, her glasses unfog, briefly revealing her eyes before they fog up again.
 * Like with Pyra's fighter model and Mythra's appearance in Smash as a whole, Brighid's outfit as a background character has been modified from Xenoblade Chronicles 2 due to Ultimate's lower age rating, covering up her midriff and legs. However, she remains uncensored in "cutscene" footage in Pyra and Mythra's reveal trailer.
 * The World Tree, a location in the original game, can be found at the beginning of the stage, when moving the camera to the left side. This applies to both its default form and its Ω and Battlefield forms.
 * The tree will later be unviewable from the camera after a couple minutes, but will appear on-camera after ten.
 * Cloud Sea of Alrest has the longest background animation of any stage in the series, lasting roughly 15 minutes before looping.
 * If at least one fighter is standing on Azurda's head, he will not turn to look at the background unless they move away.
 * Despite the house on Azurda's back only existing at the beginning of Xenoblade Chronicles 2 and the Titans forming new landmasses at the end of the game, Azurda claims that "[he misses] this old body" in Pyra and Mythra's reveal trailer, implying that the stage is intended to take place after the end of the original game (where he regenerates into his Titan form).
 * The following Assist Trophies cannot appear on this stage: Moon,, Ashley, Burrowing Snagret, Devil, Vince, Dillon, and Squid Sisters. Additionally, the following Poké Ball summons cannot appear on this stage: Alolan Vulpix, Alolan Exeggutor, Fennekin, Pyukumuku and Marshadow.
 * picks up wool blocks instead of dirt blocks on this stage.
 * Masahiro Sakurai showed an early version of Cloud Sea of Alrest in a YouTube video along with several changes made before release:
 * Sakurai suggested the cloud formations be changed to look more natural.
 * Sakurai deemed the sway the stage possesses too extreme initially, and suggested it be toned down.
 * At one point, the various windmills on the stage were accidentally moving opposite to the wind.