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 classified as class-10 zerg flyers and are the largest in terran records, even larger than a mothership, and have been referred to as "moon sized." Leviathans possess interior evolution chambers, can store many zerg warriors within them, 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.

History
Leviathans were used by the Swarm as far back 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, a number of leviathans under the command of Broodmother Kilysa formed a blockade to prevent the Dominion Fleet from protecting the throne world.

Leviathans were used by Kerrigan when entering the Void through Ulnar in the last stages of the End War

Game Unit
The leviathan is a special zerg unit in Wings of Liberty and Heart of the Swarm. It creates airborne eggs and cocoons to spawn s and brood lords, respectively. It attacks with the four spine crawlers on its underbelly and bile swarm projectiles, and launches scourges 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.

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).