Worldsoul

A Worldsoul is the aware essence of a plane in Magic: The Gathering.

Description
A worldsoul is aware of the going ons on its surface, and can be hurt by magical means. It can manifest itself in avatars and elementals. The planeswalker Nissa Revane has been known to talk to the worldsoul of Zendikar and Amonkhet, while the worldsouls of Innistrad, Ravnica and Kaladesh posed difficulties to her (Innistrad due to Nahiri's cryptoliths, Ravnica due to its heavy urbanization and Kaladesh due to its unfamiliar Aether cycle).

Alara
On Alara, Progenitus is the avatar of the worldsoul.

Amonkhet
Nissa Revane was able to contact Amonkhet's soul and learned that it suffered under a terrible curse.

Dominaria
On Dominaria, Gaea is sometimes believed to be its worldsoul.

Kaladesh
Nissa felt that Kaladesh is structured. Cyclical. Its soul might be represented by the Great Conduit.

Kamigawa
O-Kagachi is the very first kami, as old as the plane itself.

Ravnica
The Dryads of the Selesnya Conclave are believed to be in contact with the worldsoul, Mat'Selesnya.

Serra's Realm
Urza collapsed Serra's Realm worldsoul into the Weatherlight's powerstone core, giving it enough power to travel the planes.

Zendikar
Nissa Revane, the "Worldwaker" communicated with Zendikar's soul. Ashaya, the "Awoken World", was its elemental manifestation.

Plane-less worldsouls
After the destruction of a plane its essence or soul survives as an entity that can attach itself to other planes or to planeswalkers. Two such entities, (the Bog Entity and Davriel's Entity) were encountered on Innistrad.