This quest can be started when arriving in Kairo. On the market screen, go north-east (the trading center is to the west), and climb up the waterfall. Inside the building on this island, you can talk to a man who is convinced that Kairo is going to fall from the sky. If you agree to help him prevent this, he will ask that you look for an item called the "Sky Orb".
Much later in the game, you will come to the town of Vestryka. Here, go to the north-eastern part of town and enter the large building that looks like a mansion. Talk to the man inside, who will talk about trading his Sky Orb for a Lava Golem's Eye. This is a key item that will drop from the Lava Golem enemies in the area, but only after you've spoken to the man and activated the quest.
Simply defeat Lava Golems until one drops an eye, and return to the man. He will trade you for the Sky Orb. Use the Memory Teleportal in Vestryka to teleport to Kairo. You can now give the Sky Orb to the man, which will give you this achievement. Additionally, he will also give you the Star Map, required to complete the all the trading center quests in Kairo.