While tserevna-type XMs are slightly rarer than czar-types, they are more highly valued for two reasons. The first is that their adult form, the Ladja, is a more useful all-around unit than the Slon. The second is their quicker maturation time into their perfected form - on the order of ten years rather than half a century. Despite this, there are very few fully matured tserevna-type XMs in existence - a lucky thing, as the fully-evolved Ferz is one of the most fearsome units ever deployed during the war.
Notable for its lizard-like body structure, the Ferz is vastly stronger than the Ladja from which it grows. Notably, it right arm grows out of proportion with its left, developing into a massive three-fingered claw capable of grabbing and crushing an AT it gets a grip on. This arm is also the source of the Ferz's most dangerous ability - its control of its alien energy is far greater than the Ladja's, allowing it to project its right hand's reach up to nearly half a kilometer away. Each claw is sharper and more durable than the strongest bladed weapons of the Kerykeion line - the saying goes that once you're caught by those claws, it's all over.
In addition to its arm's peculiar abilities, the Ferz is capable of all the same techniques as the Ladja, assisted in its movement by its digitigrade legs and wheel-assisted feet. Like the Slon, the wheels are biological, but unlike it they simply assist in ground movement. The XM is capable of utterly enormous jumps, allowing it to even attack airborne units.
Even among the Ferz, one in particular stood out during the war - this model belonged to Sealt Arris, who served under Pomfret Akumu on the Patient One until the Korol incident resulted in their positions being reversed. Notable for her cheetah-like facial birthmarks as well as her rather feral countenance, Sealt was often known as "Fastcat", and proved herself a thoroughly competent captain. It is believed that she in fact aided Pomfret in getting around the permissions needed to pilot the Korol, but no evidence exists. She did not deploy personally until the ship's pursuit of the Arbalest led to their descent to Earth, at which time her Ferz repeatedly proved itself an equal match for Yui Laryandor's Pheora. Their last encounter led to the Ferz being destroyed. After the war, Sealt would have the custom unit Gilgamesh created to her specifications, which based many of its design concepts off of the Ferz.
This is the last of the XMs save for the Grandmaster, which a friend of mine is building rather than myself. After this, I have a new appreciation for all you reverse-jointed builders - it's hard work to get something like this to be anything stable. Last up is the White King, and it's gonna be the big one.