The Swarmlord is physically similar to a normal Hive Tyrant. Indeed, the only way one can tell the difference between the two is that one (the normal Hive Tyrant) carries a vast array of weaponry from the Tyranid arsenal, whereas the other (the Swarmlord) carries a set of four Bone Sabres, much more powerful versions of the Bone Sword used by some Hive Tyrants.
Since the Tyranids first battle against the Imperium of Man, the Swarmlord has been seen a total of seven times, two of which were during the Battle of Macragge.
- Tyran and Thandros - The Swarmlord led the final attacks on these two worlds during the Imperium's first contact with the Tyranids.
- Macragge - Cold Steel Ridge - The Swarmlord led Hive Fleet Behemoth against the Ultramarines chapter of the Space Marines, almost killing their chapter master, Marneus Calgar, and killing every other Ultramarine in the area. Calgar escapes with the help of the veterans of his honour guard.
- Macragge - Polar Fortress - The Swarmlord also led Hive Fleet Behemoth's assault on the Polar Fortress. In the end, the Swarmlord and its forces were slain, at the cost of the Ultramarines First Company.
- Holdur Sector - The Swarmlord led Hive Fleet Leviathan in the swiftest and greatest planetary invasion of the hive fleet's existence. Within four months, the Swarmlord oversaw the absorption of at least two dozens worlds, only stopping when it reached the Ork-held planet of Octarius.
In addition to these, it has also been responsible for the destruction of the Bryynar race, the consumption of all life in the Megyre system and the consumption of the Ork WAAAGH! Gorgluk.