Tree-dwellers were the monkey-like sentient creatures of Channelwood. They built villages of huts half-way up the grand trees, 10 meters above the ground.
Legends say that when their island was about to collapse, the Channelwood humans sacrificed themselves to stop it. This is most likely the reason that the tree-dwellers revered humans as gods or heroes. Nearly all the humans died out. The last survivor was revered and had a seat next to their leader's throne. The tree-dwellers and the last survivor expected the coming of another human.
When Atrus linked to that Age, the tree-dwellers recognized him as the one they were sure would come. They worshipped Atrus and offered him food and objects of affection. They were also enthusiastic when they met his sons, Sirrus and Achenar. Atrus warned his sons not to take advantage of the reverence towards them. One day after Atrus had arrived, the last human survivor in Channelwood walked off a treetop path to his death.
When the brothers grew evil, Channelwood was one of the Ages they plundered tyrannically. They established themselves in palaces among the highest levels of the trees. Achenar pretended to be a god and used an Imager to command the creatures, whom he tortured and slaughtered.
The tree-dwellers spoke a language of their own which Atrus started to learn; his sons managed to pick it up faster than he did. The Imager messages made by Achenar and used to deceive the tree-dwellers were recorded in that language.
Their leader lived in an enormous hut garnished with bright metals. He dressed in many exotic, colorful fabrics.
The tree-dwellers had developed some sort of alchemy. They cremated the body of the old man by employing a potion which easily caught fire and created a variety of inks for Atrus to use in his time in Channelwood.
They also had a sense of humor: as a practical joke, they insisted that Atrus use their inks for his journal. Months later he discovered that it changed various colors, and they laughed and howled when Atrus asked for an explanation.
There is a stuffed ape head adorned in the Mechanical fortress; it is possible that it's a severed head of a tree-dweller, as indicated by the bloody chopping block and cleaver in Achenar's cache, as well as the fact that they slaughtered all of the inhabitants of the ages.