Treeman

Treemen are massive humanoid creatures that resemble upright walking trees. They are considered a legend by most Old Worlders and the few that believe in their existence think them long dead. They are not gone, but those that remain dwell exclusively within the forest of Athel Loren.

Indeed, there are those who believe the Treemen are Athel Loren. They seldom venture beyond the forest for any but the direst reasons, and Dryads frequently accompany them when they do so. The Treemen are wise and will not engage in battles they cannot win unless they have no other choice. All the creatures of Athel Loren obey them without question, which grants them a great many beast allies, to say nothing of the Wood Elves. To stand against the wrath of a Treeman is to face the fury of nature unleashed. Survivors often dread going into the woods for years afterward, many of them becoming city dwellers permanently.

Source

 * Warhammer Fantasy RPG 2nd ED -- Old World Bestiary (pg. 110).