Elack was a male leviathan - a living ship like Moya. He was partnered with his unnamed female Pilot (John Crichton referred to her as "Your Ladyship", "Sweetheart" and "The Mother Teresa of the Uncharted Territories") for over 350 cycles prior to Crichton's arrival. Elack was very old for a Leviathan; he and his Pilot were traveling to the Leviathan "sacred space" to live out their remaining days when Crichton originally sought refuge on board.
Stranded in his fueless module and despairing that Aeryn Sun deserted him and that Moya was sucked down a wormhole, John found refuge on Elack. Since Elack was dying, John had to try to find Moya to survive. John adopted one of Elack's DRDs, painted it with the colours of the French flag and taught it to play the 1812 Overture to keep him company; eventually naming it, appropriately, 1812. Not knowing if or when he would get off Elack, John passed his time scribbling out wormhole formulas on Elack's walls and cargo boxes while getting drunk on the still he created from the things found on Elack.
Whilst occupying himself with his formulas and seeing how drunk he can get and still function, a small ship crashed into the cargo bay. This ship carried Sikozu, a Kalish, who had been helping a race of Leviathans hunters named Grudeks find Leviathans, from which they harvested toubray tissue, leviathan neural cluster tissue consumed by sentient beings to enhance higher brain functions. Closely following Sikozu, a large Grudek vessel recklessly crashes into the side of Elack, depositing a crew of hunters. John had to defeat the Grudeks to save Elack and the pilot from death; Sikozu reluctantly agreed to help. Eventually Rygel and Chiana found Elack and come aboard.
After defeating the Grudeks, John and crew concentrated on finding Moya. Elack's pilot founds Moya's last location above the planet Arnessk and traveled there to hopefully join up with her. Although Moya was no longer above Arnessk, her remaining crew (Jool, D'Argo, and Noranti) were on the planet where Elack's crew subsequently joined them. In the meantime Commandant Grayza and Captain Braca (recently promoted) discovered that John was now on Arneesk and landed multiple Peacekeeper ships on the planet, along with a very subdued Scorpius. Confusion and conflicts ensued, with the upshot being that Moya's crew required Elack's assistance to escape the Peacekeepers. Still onboard Elack, Rygel convinced the Pilot to convince Elack to help their escape by crashing into the Peacekeeper ships on the planet. Despite Elack's desire to die in the sacred space, he agreed to help. With Rygel still onboard and Elack and the Pilot delirious, Elack began a premature plunge into Arnessk. Just as the Leviathan was about to crash into Arnessk, Rygel escaped in one of Elack's debilitated pods and Elack's pilot passed out. Elack hit the ground, tumbling repeatedly and smashing all but one of the Peacekeeper ships before completely disintegrating.