The Black Garden is a location isolated from time and space on Mars. The Garden houses the Black Heart, an entity linked directly to the Darkness. The Vex collective in control of the Garden is the Sol Divisive.
The true purpose and nature of the Black Garden has been up for debate among the renowned scholars of the Tower for some time. A Thanatonaut Warlock by the name of Pujari experienced a vision of the Black Garden, noting that the "Garden grows in both directions. It grows into tomorrow and yesterday. The red flowers bloom forever." and "There are gardeners now. They came into the garden in vessels of bronze and they move through the groves in rivers of thought." During this vision, a flower shaped like a Ghost attempted to sway Pujari to the Darkness, claiming that he was a "dead thing made by a dead power in the shape of the dead. All you will ever do is kill. You do not belong here. This is a place of life."
There are three known entrances to the Black Garden. One is located in the Valley of the Kings in the Meridian Bay on Mars. This entrance requires the activation of a Vex Gate Lord to open. Another lies in Tharsis Junction; this was created when an Echo of Oryx burrowed into the Garden to let the Taken in. A new portal was recently discovered underground on the Moon.
Pujari was the first to see the Garden, though he himself never set foot there; he experienced it through a vision. Pujari's vision showed that the Vex were a creation of the Garden, after life within called out a question to which the Vex are the answer.
Uldren and Jolyon
The first known expedition into the Garden was conducted by Prince Uldren Sov and Jolyon Till. Uldren and Jolyon provoked the Cabal into attacking the Gate, forcing the Vex to respond. Thus the Vex were tricked into opening the Gate so that they could enter.