The Treant is the Dungeons & Dragons depiction of the iconic treeman monster. Stolen shamelessly from the depiction by J.R.R. Tolkien, Gary Gygax changed the name from "ent" to "treant" in order to avoid legal disputes, much the same way that hobbits were turned into halflings.
Treants are massive trees with the ability to walk around and talk. They consider themselves the guardians and protectors of their non-mobile brethren, and thus defend the woods, forests and jungles from use by humanoid races.
Although usually typed as Plants, for obvious reasons, Treants have a tradition of being associated with fey creatures, mostly because those creatures are also typically portrayed as being close to nature and sworn to its defense. Treants were even a playable race in the Basic D&D supplement "Tall Tales of the Wee Folk", a splatbook dedicated to fey PC races.
In AD&D, several known variants of Treant include:
The Lyrannikin, also known as the Black Treant; a Oerthian treant who has succumbed to hatred, rage and malice, turning into a murderous protector of the wilderness.
Ravenloft is home to malevolent, horrifically corrupted Evil Treants, of which the worst and most infamous is Blackroot of Tepest- a once-noble oak tree that was turned into a vile perversion of its former self by the Sisters Mindefisk. These creatures are so monstrous that they have been known to defy death itself and return as horrible Undead Treants.
Dungeon Magazine #61 includes the Greater Treant, which is basically a bigger, stronger, more magical version of the treant.
|Dungeons & Dragons 1st Edition Races|
|Basic Set:||Dwarf - Elf - Hobbit - Human|
|Creature Catalog 1:|| Brownie - Centaur - Dryad - Faun - Hsiao |
Leprechaun - Pixie - Pooka - Redcap - Sidhe
Sprite - Treant - Wood Imp - Wooddrake
|Creature Catalog 2:|| Faenare - Gnome - Gremlin - Harpy |
Nagpa - Pegataur - Sphinx - Tabi
|Creature Catalog 3:||Kna - Kopru - Merrow - Nixie - Triton|
|Dragon Magazine:|| Cayma - Gatorman - Lupin - N'djatwa |
Phanaton - Rakasta - Shazak - Wallara
|Hollow World:|| Beastman - Brute-Man - Hutaakan |
Krugel Orc - Kubbit - Malpheggi Lizard Man
|Known World:|| Bugbear - Goblin - Gnoll |
Hobgoblin - Kobold - Ogre - Troll