You know about all those trees you keep planting, chopping, burning, or the animals you slaughtered in the forests for whatever reason you may have, however it's a bad choice. The reason doesn't matter, as long as you harmed the forest, you shall pay for your crimes! This is a boss I made up. It only appears if you chop enough trees or kill enough creatures in the forest (good or bad) within a lifetime. Think before you kill anything in the forest and definately don't start a fire!

Combat(I decided to be flexible for most RPGs, but I'll reference WoW some
Status effects such as life drain and poisening result in him using purify. Negative effects have no effect on this boss. Every minute a treant appears to attack and they get stronger every 3 minutes. During Phasees 1 and 3 anyone who is outside of a 20 yard radius will be dragged close up to him and damaged by strangling vines.

Phase 1: For the Wilds!
Poisen spores are scattered and boss has increased physical attack. Players also suffer damage over time. Poisen spore effects cannot be removed.

Phase 2: Nature Give me Strength!
You must kill 4 treant guardians in four corners in order to break a barrier the forest lord set up to stop him from healing himself.

Phase 3: The Forest Shall Have Vengeance!
Boss is enraged and fights with 5 treant minions and higher attack, defense, and attack speed. Poisen spores are in effect again. This only happens when boss has lower than 20% health.

Strategy I had in mind: The goal is to kill this boss fast. His health isn't very high or low. You want mostly close combat damage dealers and AoE heals. Big and quick damage is needed for this to be a fast fight. Tanks should never move around. Since Forest Claw has a huge swipe attacking everyone in front at a cone, the boss must face away from damge dealers.

That is a leafy kilt. There is more growing at his foot. Those vines have poisenous flowers. They will release spores thus giving a poisened dot. Eventually you will die. I gave it a leafy beard and leafy hair that kinda has a normal hair texture. He doesn't need a shirt or shoes, after all this thing was a tree before. I was inspired a little by World of Warcraft :)

Edit: I added spores to give a naturey effect and a fist weapon for more attacks.