Would you mind me having my take on this?
It's a good concept, but it's execution could benefit from more perspectives, like what I have in mind at the moment. I'd be pointless to describe, however. A sketch would be much more effective.
When I think 'trees', I quickly imagine solidity, firmness, deeply ingrained and anchored in the ground. Libra then brings to mind aspects of balance and justice. I imagine this massive tree statue just standing as a bastion, preventing entry, keeping the peace (Balance) with it's massive armoured guardian of the forest, in ways similar to the ents. This thing is (Or should be, given the elements present), in every possible conceptual core, a stout defensive wall.
Your work on the other hand looks flimsy, and if I may... Squishy and slippery. Like an octopus. It doesn't have any solidity and the armour feels as if it was left there rusting. It bends in many odd ways and it completely lacks firmness to the ground; it feels as if it could crawl and move at will, easily, like a scaled animal. There's little gesture of it being defensive -and- offensive. It's just not accomplishing much of any. Neither the defensive wall or the forth-lunging defender of justice. It's also 'small', without any qualities of grandness or epic. Like another one of those strange throned things in the forest, who could serve as normal enemies in a game.
I'm not saying you'd have to follow my vision, but this is how I observe what's before me.
Was this 'your' original intention? The pencil drawing on the first page communicates something entirely different.