Go to the east side of Lletya, east of the building with Gwir inside, and climb the rope attached to the sturdy tree on top of the cliff. Go to the north-east corner and climb into the large dead tree. In the tunnels, head north and around the bend, cross the stepping stones toward the centre, head south-east and jump the gaps, head all the way north, cross the rope and exit the tunnels. After emerging from a large dead tree, head south-east towards the hill giants. Squeeze-past the southern-most plant and the achievement will be complete.