The Astral Plane is Gargos' stage in Killer Instinct (2013). It is the 21st (and possibly final) stage that is introduced to the game and the fourth and final stage introduced in Season 3. This stage can only be unlocked by defeating Gargos in the Shadow Lords game mode, and is the location where the tyrannical demon lord is confronted as Shadow Lords' final boss. It is also where the player battles each of the Omens in order to weaken Gargos before the fateful encounter.
The Astral Plane appears to be situated in outer space, as countless stars and nebulae can be seen all throughout the background along with a quasar which takes up the center view of the stage. The fighting takes place on a plane of rectangular, cyan colored panels floating across the cosmos.
Gargos' new boss theme, titled "Kneel to Your God", was performed by Celldweller & Atlas Plug. It is a dynamic remix of the character's classic theme from Killer Instinct 2/Gold, but much more faster, louder, and metal, truly befitting the Shadow Lord's demonic character. The new theme overall ranges into the genre of both power and speed metal.
- The Astral Plane appears to be a tribute to the secret Sky Stage areas from the previous Killer Instinct games, though it lacks a Stage Ultra.
- This stage, along with Kim Wu's Chinatown Brawl, Arbiter's Arena of Judgment, and Tusk's Icehaven, are the only stages created for Season 3.
- The Astral Plane is the second unlockable stage in Killer Instinct (2013), the first being the Shadow Tiger's Lair back in Season 1.
- This is the only stage in KI 2013 in which the overall environment doesn't change dynamically as the battle rages on, especially during an Ultra Combo.
- This stage and the Arena of Judgment are the only stages in the KI franchise that are not located on Earth.