Treants are powerful, ancient trees and more primitive forms of the wise Ancients that served under Cenarius in ages past. They are closely affiliated with druids, and are often seen accompanying powerful druids and keepers of the grove. Many treants were driven mad during the Third War. The destruction of the forests, as well as demonic corruption, has driven them to lash out at anyone that approaches. Treants resemble large moving trees with faces.
This creature looks to be a short, angry tree-men. Its branchlike arms end in three-fingered claws. Treants are small, tree-like beings. They are rarely seen in times of peace, but in days of conflict they patrol the forests and fling themselves at nature’s enemies. Treants do not speak, but they understand Darnassian.
Little is subtle about a treant’s tactics. They charge their enemies as soon as they can, slashing with their wooden claws.They are also known to use nature spells to a certain degree.
The lowest level treants are found in the southern reaches of Sunstrider Isle, from the Shrine of Dath'Remar all the way to the bridge. The lowest level hostile treants are the Level 9 Withered Green Keepers in the Eversong Woods. Level 13 Corrupted Treants that can be found in Middenvale on Bloodmyst Isle. Level 26 Corrupted Treants can be found just south of the border of Felwood, in Ashenvale. In Felwood, treants can be found in Irontree Woods, roughly level 52. There are a few treants which are for the most part passive in Feralas. Many hostile corrupted treants can be found in Dire Maul in the east wing. There are also treants defending Darnassus.
Technically there are treants in Terokkar Forest: They were once trees, but following the explosion in Auchindoun, the magic corrupted them and they became animated. In Outland you (as an Alliance player) introduce treants into the ecosystem in Blade's Edge Mountains, while the Cenarion Expedition seeks to heal lands once belonging to the treants and ancients. Treants have also been spotted in Crystalsong Forest and are both neutral and hostile.
In World of Warcraft
Treants have always been present, both good and bad, in WoW. Additionally, the 41 point talent in the druid Balance tree, Force of Nature, allows a Balance druid to summon 3 treants to fight on their behalf for 30 seconds (or until they or their master are killed) and has a 3 minute cooldown. Similarly, the top talent in the Restoration tree is Tree of Life Form, which allows Resto druids to become treants.
Quests introducing treants to Outland
They are listed as elementals in World of Warcraft and ambulatory plants in the RPG.
The Treants were likely inspired, in both name and overall nature, by the Ents, a powerful race of sapient trees in the works of J.R.R. Tolkien. "Treants" and variants appear in various fantasy media. The Ents themselves were probably inspired by the tales of talking trees found in various world mythologies, though the Ancients would be a closer Warcraft parallel to the mythological variety.