A Bog Beast
As the name suggests, bog beasts are massive, shambling monsters that are half plant and half beast. Little is known about these secretive lords of the swamp and forest except that they are territorial and quite agressive. Explorers have recorded stories of their great strength and resilience to harm. Unlike animals, they reproduce by seeds. They are elementals of nature. In some ways they reflect the natural order of plants and animals.
When roused to anger, they fight with great power and fury, using their strength to slam into their enemies, crushing opponents' defenses with their fists and whatever large objects they can throw at them.
The Bog Beasts of Teldrassil, called timberlings, are also reflect the natural order of plants and animals on the great tree.
So it is disturbing to see how angry the timberlings have become. Another symptom of the timberling's disease are tumors within their bodies, filled with a poison.