Site 11 key
In the anteater hunt, in the Lhusu mines, you have to rescue some stupid kids that ran into the monster infested mine. After you kill the Anteater, go back to the part of the room where there's a huge opening in the floor, and you should see the kids(it's the area right before the anteater). They will say that they dropped the key, and that it probably washed up on a shore some where far away.
After you go back and talk to their mom to get the reward, find a gate crystal, and warp to the Phon coast. Then go North, and you should be on a hill with a man sitting against the wall. Talk to him, and he should say that he fell from the city Bhujerba, and landed here. Then look to the right of him, and there should be a glowing light. Click on it, and you'll receive the site 11 key, which you need in order to reach Gilgamesh the second time.