After becoming a Kon, there are two maturation paths the alien lifeform which XMs are created from can take. The first is for the cocoon to split open after roughly five-ten years, from which emerges a tsarevna-type adult - these are Ladja, which if allowed to mature to perfection becomes the vastly more potent Ferz. The second is for the alien to grow together with its pupa over ten years, the cocoon eventually forming body armor. The result is the czar-type adult - a czar that reaches perfection can become a Korol, while the base adult instead becomes the Slon. The tanks of Crow's army, the Slon is a powerful ranged bombardment unit.
The Slon is an example of the extremely mutable biology of the XM - its wheels are in fact organic in nature, with two on each of its four short legs. Each leg is capable of independent movement, allowing the tank to raise itself up on its forelegs for anti-air attacks. Its only weapon is the mega launcher on its back, one of the most powerful cannons seen during the war - it requires 10 seconds of charge time before firing a tremendous beam of swirling red and black capable of shredding entire rows of enemy forces in a single shot. The cannon's charge time and enormous power means that Slons are typically used as anti-fortress weapons, a small complement of Peskas protecting the unit while it fires on a large or otherwise stationary target.
Besides the mega launcher, the Slon has little in the way of offensive capabilities - however, it is not entirely defenseless, as its bulk hides a surprising amount of speed. Due to its enormous weight, it is also often capable of simply crushing an enemy which it can land on or knock down.
One Slon of note was the secondary unit of choice of child soldier Kareita Afrit, used in situations where her Kon was not practical for the mission at hand. This unit was the most successful of its kind during the war, though like most of its kin it was disabled during Rei's last sortie. Her later custom unit Ifrit would incorporate qualities from both XMs into its design.