When you get to the Spirit Forge and the Elder God is closing it of with his tentacles, do the following. First, jump down and slash where the four connect. Next, climb out and use your Dark and Light Reavers in the holes on the ground (beneath the glowing runes). He will shout and drag the front deeper. Go down and slash. Use Earth Reaver to help get back up to the top. Do the same thing for Water and Fire. He will retreat deeper. Slash him again. Use Earth to sink and slash, Water to freeze the waterfall, and Earth to create to rock bridges. Climb to the top and stick the Air and Earth Reavers in to ignite the Forge. Then, just float down and get it.