The Thirst is a villain in the DC comics.
The First is a composed of dry river mud, the mystical "brother" of a being an ancient goddess known as the Waterbearer. The Thirst has preyed on the deities who have watched over the Secret Sea, a metaphysical realm composed of the shared imagination of humanity; for a millennia, absorbing their power.
When Aquaman became the guardian of the Secret Sea, the Thirst set its sights on the hero. The evil and magical parasite battled Aquaman several times, attempting to drain not only the rivers of Earth and the magical waters of the Secret Sea of all life, but the Sea King's very essence as well. In their final battle, Aquaman and the Thirst merged into a single, monstrous being. When Aquaman stopped fighting the Thirst and surrendered his control to the light of the universe, the evil parasite was consumed by the holy power and seemingly destroyed forever.