The Swarmlord is a uniquely powerful Tyranid bioform based on the Hive Tyrant strain and it is the most powerful synpase creature ever created by the Hive Mind. Amongst the billions of creatures created by the Tyranid Hive Mind, there exists one as old as the Tyranid race itself, the ultimate conduit through which the Hive Mind's implacable will is enforced. This creature is to a Hive Tyrant what a Hive Tyrant is to a Termagant. It is a monster of darkest nightmare that has preyed on empires and overseen the extinction of entire civilisations. It is a legendary destroyer of worlds and its names are legion. It is the Tyrantlord of the Hive Mind, the Herald of the Great Devourer and the Destroyer of the Kha'la Empire.
To the Imperium of Man, the latest interstellar civilisation to face this ancient predator, it is the Swarmlord, and it represents the greatest Tyranid threat to the galaxy. The Swarmlord is the pinnacle of the evolution of the Hive Tyrant bioform, a truly unique monster. The Swarmlord is essentially immortal, like a Hive Tyrant, as once killed it is remade by the Hive Mind with the exact same experiences, memories, personality and knowledge, in essence becoming stronger than its predecessor every time because of its prior lives. But unlike a Hive Tyrant, the reincarnation of the Swarmlord appears to be a stress-induced response that is triggered only when conventional strategies of the Hive Mind fail and greater resourcefulness and tactics are needed.
To this end, the Swarmlord possesses more mental autonomy from the Hive Mind than any other Tyranid corganism, and its connection with the Hive Mind is so strong it can emerge amongst any Hive Fleet, transcending any physical limitations separating the different fleets. The Swarmlord has aeons of battle experience and bloodshed to draw upon. As weapons the Swarmlord wields four Boneswords, crackling with disruptive power, that are capable of slicing through adamantium and even force fields as if they were nothing. They differ from commonly seen Tyranid Boneswords in that each sabre-like blade has a crystalline growth, not indigenous to the Milky Way Galaxy, at its core that partially protrudes through the blade's serrated surface. The Swarmlord can parry with these sabres at such speed that its foes find it all but impossible to inflict a hit on the creature.
- Tyran and Thandros (745.M41) - The Swarmlord leads the final assaults against Tyran and Thandros during the Imperium's first contact with the Tyranids.
- Battle of Macragge (745.M41)
- At the Battle of Cold Steel Ridge on Macragge the Swarmlord directed Hive Fleet Behemoth to defeat every one of Marneus Calgar's and the Ultramarines' tactics. Calgar himself was almost killed by the Swarmlord, but managed to escape alive with the help of his Honour Guard while the Swarmlord killed the Commander of the Guard Aloyseus.
- The Swarmlord led the attack on the polar fortresses of Macragge defended by Captain Invictus of the Ultramarines' elite 1st Company. In the end, the entire 1st Company was killed and official Imperial reports listed the Swarmlord as slain at that time.
- Unknown Date.M41 - Scouring of the Megyre System
- Unknown Date.M41 - Destruction of the Bryynar race
- Unknown Date.M41 - Consumption of the Ork WAAAGH! Gorgluk
- Assault on the Holdur Sector (997.M41) - The Swarmlord returned to attack the Imperium, leading the swiftest and greatest planetary invasions of the recently arrived Hive Fleet Leviathan. In the space of four solar months the Swarmlord oversaw the absorption of two dozen worlds including Talon, Chapter planet of the Storm Falcons Space Marines, and Endragiga, the site of a major orbital shipyard of the region. Later Imperial reports indicated that the Swarmlord was leading the Tyranids' assault on the Orks of Octarius.
- Devastation of Baal (ca. 999.M41) - The Swarmlord was spawned anew to lead the forces of Hive Fleet Leviathan that descended on Baal, the homeworld of the Blood Angels Chapter. It was slain in personal combat by Commander Dante, Chapter Master of the Blood Angels.
- Codex Adeptus Astartes - Blood Angels (8th Edition), pp. 21-23
- Codex: Tyranids (8th Edition), pp. 28-29
- Codex: Tyranids (6th Edition) (Digital Edition), pg. 59
- Codex: Tyranids (5th Edition)
- Devastation of Baal (Novel) by Guy Haley