Here's a video of the location and walkthrough on how to do this.
1. Walk left from Arkos until you find a wall you need to break, and you will need to do 2 boss fights to be able to break this wall.
2. Gather all four skeletons as best you can.
3. Figure out your damage level. The skeletons were two hit kills for me, so I hit them each once.
4. Reflect the spear or throwing axes back at all 4 skeletons.