A Leviathan is covered in extremely tough hide and its body possesses numerous tentacles that it uses primarily for swimming, though it likely also uses some of these appendages for seizing prey. The bottom jaw of the beast has two rows of stone-hard teeth and one row on the upper jaw. The creature's tongue splits into two thick, snaking tentacles which are covered in barbs.
Hollow Storm Edit
Before being encountered by the COG, the Leviathan territory was avoided by the Locust at all costs, due to the danger of the beast. The Stranded who had headed into the Hollows to seek shelter from the war had some knowledge on them. The Stranded Chaps warned Marcus Fenix and Dominic Santiago about the lake under Mount Kadar and how it was the only way to reach Nexus. Left with no choice but to advance, the soldiers commandeered a Locust craft and began making their way across the water towards Nexus. They fell under fire by multiple Locust gunboats, and during the confrontation they got their first view of the Leviathan as it pushed their raft towards the edge of the lake. After boarding and capturing one gunboat while the other retreated, they fell over a massive waterfall. Once at the bottom, the Leviathan, which had been stalking them beneath the water, killed the two Manglers that moved the Gunboat and began to attack it, along with the Gears on board, with its tentacles. The two soldiers were able to cut the offending tentacles off with their chainsaw bayonets before they sank the gunboat. Marcus determined that the Leviathan's weak point was its eyes and the inside of its mouth. When the Leviathan bit onto their boat, they forced its mouth open by shooting it in the eyes, and threw bolo grenades down its throat, killing it.
Lambent Pandemic Edit
At the beginning of the Lambent Pandemic, three Lambent Leviathans attacked Vectes carrying Polyps. The first was killed after a King Raven emptied an entire belt of chain gun ammo into its head. The second was killed by a combined torpedo attack from the submarines Clement and Zephyr, and the third and final Leviathan was killed by a blast from the Hammer of Dawn.
Another one later attacked New Jacinto. COG forces attempted to use the Hammer of Dawn to defend themselves, but the satellites failed, forcing them to find another way to destroy the creature. It was eventually chased to the surface by depth charges and killed by a grenade being thrown down its throat.
In a separate incident, yet another attacked the CNV Sovereign and was killed after Damon Baird manuevered a cargo container of Tickers and dropped it on the Leviathan. The resulting explosion destroyed the Sovereign and Centennial Bridge. This one was said to be twice the size of the other Leviathans.
A normal Leviathan attacked Delta Squad's submarine on its way to Azura. After dealing with a swarm of Manglers, it appeared in front of Delta in the vegetation they were hiding in. It chased the sub through a minefield and through narrow archways where it tried to bite through the hull. The Gears retaliated by taking advantage of its gaping mouth and directing their fire into it, while the Leviathan got stuck in the archways of the underwater cave. Unable to reach the sub, it resorted to attempts to crush the submarine with its tentacles. The Gears kept shooting to fend it off, and it was finally killed when it caused the tunnel rock to collapse and crush it while attempting to take down the sub.