Wurm
Gigantic, limbless, ground-dwelling green-mana creatures (exceptions do occur), wurms are related to dragons. According to legend, the ancestors of the wurm rebelled against their fellow dragons. After losing, they were thrown to the ground, beaten and stripped of their wings. They generally dwell in forests, convenient for satisfying their mammoth appetites. There are two kinds of wurms, the Worm-like and the serpent-like. The worm-like wurms are almost like annelids and have four huge incisors in their huge circular mouths. Their shape is largely cylindrical and they are great burrowers. This kind of wurm is common on the Krosan forest. The Serpent-like wurms are much more reptilian; they have jagged mouths, two eyes, and normally an array of horns and spikes along their scaled body. Serpent-like wurms rarely dig tunnels, for they are active predators and can ambush uncautious prey. A skilled wizard can summon or tame any of both kind of wurm at will. The great amount of mana is an issue to reckon with when summoning wurms however. All the wurms are huge creatures that measures around a hundred feet long and are among the biggest forest creatures.
Wurms are also found in the urban Ravnica, but usually under abnormal circumstances. The Selesnya Conclave use specially tamed and trained wurms for offensive maneuvers. The Golgari carnomancers are sometimes hired by the Orzhov to call forth the wurms from the underground. It would appear that the Gruul Clans have a close association to the wurms.
(Argothian Wurm)
Read more about this topic: List Of Species In Magic: The Gathering