Saproling
Native to Dominaria, Rath, Mercadia, Jund, and Ravnica. Saprolings are carnivorous, primal, fungal creatures whose form varies wildly across both the planes and the centuries. Initially created in the Havenwood of Dominaria's Sarpadia as a side-product of the Thallids, Saprolings were originally little other than small clumps of fungal matter that scurried around their larger Thallid cousins. Despite their artificial origins, they adapted quickly to the plane's ecosystem, somehow migrating from Sarpadia (without the Thallids) and becoming an established part of the ecology of the Yavimaya Forest, the largest on Dominaria. Here they evolved into greasy, ferocious worm-like creatures ranging in scale from the size of a small dog to that of a rhinoceros (This breed was also the dominant strain on Rath and also on Mercadia, where the saprolings were a major menace to outlying farmers).
After Yavimaya was decimated during the Phyrexian Invasion, the Saprolings spread further afield and continued to evolve, slowly reverting to their original ambiguous, fungal forms. The decaying nature of Dominaria led the Saprolings to evolve a tolerance for dead matter, and the considerable quantity of this resulted in a huge explosion in the Saproling population of the plane. The Saprolings started to become an ecological threat in Rift-Era Dominaria, spreading through rotting forests as a thick, squealing blanket of squirming fungal matter.
On Ravnica, Saprolings are small, non-carnivorous plant-creatures whose form depends on the guild that controls them. The vast majorities are Selesnya creations and represent young, developing plant elementals. They are grown around glowing green crystals that provide all the sustenance they need. Other guilds produce their own varieties; Golgari rot-farmers grow Saprolings from corpses, while Simic biomancers grow them from whatever tickles their fancy.
In the game, Saprolings are unique for being a long-lived and popular creature type, yet one which has no actual printed creature card. Instead, Saprolings are universally "creature tokens" - false cards created by the effect of another card. They have an ardent cult following among fans, and have frequently seen high-level tournament play due to the abilities of some cards to generate multiple Saproling tokens either at once or over several turns. With the Alara Block, many tokens cards have been printed, including Saprolings, giving an actual artistic impression of the creature.
(Sprout Swarm, Golgari Germination, Spontaneous Generation, Selesnya Evangel)
Read more about this topic: List Of Species In Magic: The Gathering