Terrestria is the plane on which the planet Earth is located.
EDIT: Due to limited Magic information, the best assumption is that planes are individual planets. No other information can be garnered from the true Magic: the Gathering storyline. The best explanation for our universe being in the MtG multiverse is billions of overlays on a gigantic plane, causing each individual cosmic body that exists in real life.
EDIT: The formation of a seperate article, i.e. 'The AoM Multiverse' is suggested.
It is commonly accepted that a plane is not a planet, though in most cases the focus of a plane will take place on a particular planet within this plane. The confusion arises in that most planes are confused with planets, due to the fact that most planes are named after their primary planets.(). Each plane is a seperate 'universe' however, the word itself has the stigmatic effect of only meaning there can be one 'verse'. Each 'verse' is a plane, within a wider multiverse. This given it means that any number, and any variant of a plane is possible within the multiverse, it can be said that the Magic multiverse contains an infinite number of planes. (). As part of the possibility, and as is used in these storylines, Terrestria is part of this multiverse.
|Past Planes of AoM|
|Planar System(s):||Syndicate System|
|Plane(s):||Arcanis | Mirrodin | Terrestria | Focturna | Sahrahlas | Yorfallia | Avernus|
|Future Planes of AoM|
|Planar System(s):||Chaos System|
|Plane(s):||Furcht | Arcanis | Sahrahlas | Avernus|