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 fuelless module and despairing that Aeryn Sun deserted him and Moya was sucked down a wormhole, John finds refuge on Elack. Since Elack is dying, John must find Moya to survive. John adopts one of Elack's DRDs, paints it with the colours of the French flag and teaches it to play the 1812 Overture to keep him company; this DRD would eventually be named, appropriately, 1812. Not knowing if or when he will get off Elack, John passes his time scribbling out wormhole formulas on Elack's walls and cargo boxes while getting drunk on the still he has created from the things he found on Elack (the raw ingredients he uses to make his brew are never revealed).
Whilst occupying himself with his formulas and seeing how drunk he can get and still function, a small ship crashes into the cargo bay. This ship carries Sikozu, a Kalish, who has been helping a race of Leviathans hunters named Grudeks find Leviathans, from which they harvest 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 must now defeat the Grudeks to save Elack and the pilot from death; Sikozu reluctantly agrees to help. Eventually Rygel and Chiana find Elack and come aboard.
After defeating the Grudeks, John and crew concentrate on finding Moya. Elack's pilot finds Moya's last location above the planet Arnessk and travels there to hopefully join up with her. Although Moya is no longer above Arnessk, her remaining crew (Jool, D'Argo and Noranti) are on the planet where Elack's crew subsequently join them. In the meantime Commandant Grayza and Captain Braca (recently promoted) discover that John is now on Arneesk and land multiple Peacekeeper ships on the planet, along with a very subdued Scorpius. Confusion and conflicts ensue, with the upshot being that Moya's crew requires Elack's assistance to escape the Peacekeepers. Still onboard Elack, Rygel convinces 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 agrees to help. With Rygel still onboard and Elack and the Pilot delirious, Elack begins a premature plunge into Arnessk. Just as the Leviathan is about to crash into Arnessk, Rygel escapes in one of Elack's debilitated pods and Elack's pilot passes out. Elack hits the ground, tumbling repeatedly and smashing all but one of the Peacekeeper ships before completely disintegrating.