Sagar is a fictional rocky planet where the Blackstar series take place.

In the series, Earth astronaut John Blackstar, as his spacecraft after being swept through a black hole, ends up crashing on the planet of Sagar.

Despite its atmospheric similarity with Earth, the two planets are also very different from, with Sagar being inhabited by many extraterrestrial species.

The Sagar Tree, a mystical place, is ruled by the peaceful pink-skinned Trobbits. It seems that the Trobbits can tap their magic into the forcefield which lies behind the Sagar Tree. Likely, many sorcerers and magical creatures on Sagar can draw energy from a mysterious source set in a parallel plane.