Black Obelisk

The Black Obelisk, sometimes also called Black Obelisk of Vyr, was a magical construct of unknown proportions created by Vyr.

Background
The Obelisk was created by Vyr the Vainglorious as an arcane power conduit used to harness energy of Archons from other planes.

When Vyr had been killed, the Obelisk bearing his name was destroyed as well.

Apparently, the Obelisk could trap humans in its inner labyrinths, so it was either very large, or could lead to a pocket dimension of some sorts.

In-game
The Obelisk does not appear in any of the games, but is referenced in flavor text of Vyr's Amazing Arcana set and.