Bolotsar - Ruinamdei Sordibus
The Moscow Incident of 1983 transformed the area dramatically in ways noone expected. It just so happened that Soviet scientists were, in a secret facility under the city; experimenting with a new bioweapon that surviving documents refer to as "Krovibombi". Ideally, this cocktail of chemicals and microorganisms would have caused intense puss-filled tumoring in any living thing it came into contact with; resulting in a violent and bloody explosion. However, when American nukes hit Moscow; the krovibombi was released into the irradiated atmosphere and was altered. The resulting sludge would mutate all organic matter in the area and would even gain a sentience of it's own. By the time the whole mess was stable enough for researchers to survey the area, the enviroment was unrecognizable. The russian landscape had transformed into a festering radioactive swamp populated by a managerie of mutant wild-life.
The most notable of the Moscow Swamp's denizens is the Bolotsar. The Bolotsar is an apex predator in the area. They are literally walking monuments of the Moscow that once was, as the larger part of their saurian flesh is shaped over heavily irradiated ruins, namely pieces of nuclear generators and/or powerplants. While the creatures have been observed eating any and everything else in the swamp, there are no records of Bolotsar attacking human observers; even when right in front of them. Mutabiologists speculate that anything that isn't the native mutant life may be poisonous to the creatures or invisible to their senses.
So far only five individuals have ever been recorded and all of them (Save for Titanna, the only confirmed female, who was killed by a frightened soldier in 2010) are alive to this day. They are extremely elusive and it is unknown if they have or can reproduce. Autopsy of Titanna shows that a fetus was present in her womb, but it had misscarried aproximately 8 years before her death and was partially rematabolized.