The Cultivator is an ancient force of balance in the Starbound universe. It existed for aeons before the rise of the Ruin, and under its influence, harmony reigned. With the rise of the Ruin, however, the Cultivator was forced into a fight for the survival of the universe. Although it was able to seal the Ruin away from the rest of the universe, it exhausted all of its energies doing so.
Before the Cultivator dissipated altogether, it gifted six chosen races with artifacts. These artifacts, when all placed in the gate to the Ruin, will open the way, allowing the Ruin to be defeated for good.
The Cultivator is depicted as humanoid, and is implied to be astronomically large, being depicted holding or looming over planets and galaxies. Whether it actually was such a form, or if it had any physical form at all, is not established. Both known depictions of the Cultivator are located at the Ark.