[Valandil]

"How about Swamp Thing? Not only do the comics provide lots of monstrous inspiration, but it'd be cool to have, say, an independent heroic, stronger and more intelligent version of a Vine Ogre, with lots of Nature magic, named "Swamp King", performing basically the same function as Bogus, only for nature-related events"

There is. He's called Intor Vadul the ancient presence.