This is an unmissable story-related trophy that you will gain by completing the fourth chapter in the game, "Fangorn Forest".*** Spoiler - click to reveal ***You will gain this trophy upon completing the 4th chapter, as the end of this chapter requires you to defend an Ent as he destroys the camps in the forest. The "Ent" being the big tree who is on your side. The defending section itself isn't that tough, it mainly requires you to fend off orcs/goblins as the Ent destroys Siege Towers in one camp, then makes his way to the second, protecting him along the way and at the second camp to do the same as in the first.
Note: In both these camps, there'll be a side quest for destroying 3-4 mineshafts in the first and second camp with the siege towers, which you can see easily on your map/on your screen by the big silver star, you just simply bash them with your shield (Click left analog stick with shield equipped)