Leviathan

"Warning. Unidentified zerg organism detected inbound. Largest on record."

- An adjutant after detecting a leviathan.

The leviathan is a massive airborne zerg breed.

Overview
Leviathans are the zerg's equivalent of a capital ship. They are classified as class-10 zerg flyers and are the largest in terran records, even larger than a mothership, though dwarfed by an arkship, and have been referred to as "moon sized." Measurements taken by the Terran Dominion have placed the leviathan at being around 6.7 killometers long. Leviathans possess interior evolution chambers, can store tens of thousands of zerg strains within their interior chambers, and are capable of deep-space travel and can land on planets. They can operate in temperature conditions of near absolute zero and are capable of traveling through warp space. Sacs may be dropped from leviathans. Because of the sheer size, wraith sensors are unable to penetrate deep enough to see the leviathans' interior spaces.

Leviathans are typically armed with a daunting array of bio-weapons. Giant, hollow tentacles resembling those of the spine crawler can grab smaller craft or puncture the hulls of larger ships and insert zerg boarding parties. Most leviathans can launch bile swarms at their enemies, and unleash powerful bio-plasmid charges that deal devastating damage to their targets. Furthermore, coccoons birthed within the leviathan are capable of mutating into mutalisks and brood lords.

Leviathans rarely, if ever, travel alone.

History
Leviathans were once space-borne creatures before being infested by the zerg, turning them into armored carriers. They were used by the Swarm in war as early as the fall of Aiur, and at least one was present at Char in the Second Great War. During the, zerg broods in leviathans were on their way to the planet when Kerrigan was de-infested. These broods were then scattered or destroyed. Upon her return to the Swarm, Kerrigan's new base of operations was a leviathan. It would fly to different planets and land on them at her direction.

During the Swarm invasion of Korhal, Arcturus Mengsk ordered any and all Dominion troops from across the sector to return to the capital world. A number of leviathans under the command of Broodmother Kilysa formed a blockade to prevent the Dominion Fleet from entering the system. Leviathans were used by Kerrigan when the Zerg Swarm entered the Void through Ulnar in the last stages of the End War.

Years later, feral leviathans were lured to Tyrador IX via psi-emitters from the Defenders of Man. By 2512, leviathans continued to be a core part of the Zerg Swarm's stellar arsenal.

Game Unit
The leviathan is a special zerg unit in Wings of Liberty and Heart of the Swarm.

Wings of Liberty
Leviathans creates airborne eggs and cocoons to spawn and brood lords, respectively. It attacks with the four spine crawlers on its underbelly and bile swarm projectiles, and launches and bioplasmid globes dealing 500 damage. It may also put enemy units and buildings in biostasis, removing them from the fight. It may be confronted by the player in the mission "Shatter the Sky" or later in "All In", depending on decisions made beforehand. When it dies, it loses its coloration before it explodes.

Upgrades and Abilities
Despite not having a detector passive icon, the leviathan is able to detect cloaked or burrowed units.

Heart of the Swarm
In Heart of the Swarm, once Kerrigan has reached level 60 she can summon leviathans to the field, one at a time. These leviathans do not spawn brood lords, scourges or mutalisks. These leviathans also only have 1000 hit points and last 4 minutes. She has to wait 5 minutes before she can summon another one (4 minutes with ability efficiency). Notably, it can attack while moving and attack both ground and air targets at the same time.

Upgrades and Abilities
Despite not having a detector passive icon, the leviathan is able to detect cloaked or burrowed units.

Co-op Missions
Leviathans can be spawned by Abathur in the Co-op Missions mode of Legacy of the Void. Leviathans are used by Amon's forces in higher difficulties.