Ultoria

Ultoria is a location in the world of Dota 2. It is implied to be a celestial body, since it has its own moons. The lunar cycle of Ultoria's moons last for a full year.

An important battle was fought in this place, and Barathrum was sent on behalf of his master to intervene.

It's possible that this place has something to do with, seeing how it is similarly named to his title of Mars Ultor.