You'll discover many treasures in the world of Indiana Jones and the Great Circle. Very few, however, will require you to revisit other zones just to collect the items that you need. Here's our guide on how to complete The Serpent's Chest in Indiana Jones and the Great Circle.How to open The Serpent's Chest in Indiana Jones and the Great Circle - Puzzle guideThe Indiana Jones and the Great Circle Serpent's Chest is a mystery-type objective that takes place in the Sukhothai region. Specifically, you start this side quest from Voss' Camp in the northern part of the zone. Serpent's Chest location and Breathing Device requirementYou can start the Indiana Jones and the Great Circle Serpent's Chest quest by reading the note that's next to the ornate container itself. It's found inside the barracks to the right just past the Voss' Camp entrance. The note details how the Nazis are looking for ancient keys that have been lost in the Vatican, Gizeh, and Shanghai, areas that you've previously visited as part of the campaign.Before you head to those locations, though, remember that you need the Breathing Device/Rebreather sold by Tongdang, the booklet vendor in Sukhothai. This is the only way for you to survive for prolonged periods underwater, since the areas where these keys are hidden require you to swim through passageways.Here are some tidbits to consider while you're still in Voss' Camp:In the washing area/yard, you can pick up the Royal Army Uniform/Disguise. This will prevent most soldiers from turning hostile when they spot you.In the main building, you'll find Voss' own safe. Input the code 5-4-8-4 to unlock it. This nets you over 2,000 baht, more than enough to buy the Rebreather.Also in the same building, you'll come across a board game. This is the Mak-Yek puzzle.At the back of the camp, there's also the Elephant in the Room puzzle.In any case, once you have the Rebreather and you feel that you're ready, open the Travel tab on your journal to return to previously explored zones. Ancient Vatican Key mapThe map above shows the location of the Ancient Vatican Key. It's in the Necropolis area. Ancient Vatican Key locationFrom the Excavation Site, take the shortcut that leads back to the large chamber with the pool of water. Jump down and face the western wall. Swim underwater and use the Rebreather so you can reach the key. Ancient Gizeh Key mapThe map above shows the location of the Ancient Gizeh Key in the Tomb of Khentkawes I. Ancient Gizeh Key locationIn the elevator section, head through the corridor that leads to the room where you electrocuted two Nazi guards. The large section that's adjacent to that is partially submerged. Swim through the opening and move the wooden board to grab this key. Ancient Shanghai Key mapYou're one step closer to finishing the Serpent's Chest quest in Indiana Jones and the Great Circle. This time, you have to head back to Shanghai. Ancient Shanghai Key locationThis key requires you to backtrack from the rooftop where Gina flew the plane, all the way to (almost) the starting point. Specifically, it's the area with the canal and bridge. Serpent's Chest rewardOnce you've obtained all three Ancient Keys, return to the barracks in Voss' Camp. Insert each key to unlock the container. You reward, sadly, is just a single Ancient Sukhothai Relic. That seems a bit disappointing but, on the bright side, that's one more to add to your overall tally.That does it for our guide on how to complete The Serpent's Chest in Indiana Jones and the Great Circle. If you're keen on tackling other mysteries in Sukhothai, be sure to read our Mak-Yek puzzle guide and Elephant in the Room guide.You're bound to encounter many secrets, puzzles, and challenges in Indiana Jones and the Great Circle. As you continue your adventure, we encourage you to take a look at our Indiana Jones and the Great Circle guides hub.