This page will offer a walkthrough on the DLC side quest EX Treasure: Ancient Mask. This hidden treasure is a part of the first DLC, which is available by purchasing the Expansion Pass for Breath of the Wild.
How to Start EX Treasure: Ancient Mask
To begin this quest, you’ll need to find clues to the whereabouts of the treasure chest. The clues are given to you by Misko’s Journal, found in Outpost Ruins, near the Forest of Time. Then, you’ll find the journal with the clues within the ruins, near a broken wall. The journal will give clues to this treasure as well as the following:
EX Treasure: Ancient Mask Location
Once you’ve found the journal, you’ll receive the clue “the ancient mask lies at the ruins where soldiers gathered. From there the waters of Lake Kolomo are visible”. You’ll want to head to Lake Kolomo, which you can reach by fast travelling to Oman Au Shrine and then heading northeast. Then, you’ll find the treasure within the ruins near Lake Kolomo, and you’ll need to use Magnesis to pull it out from the ground. Upon looting it, the Ancient Mask is revealed to be Majora’s Mask! The Mask makes it harder for lesser enemies to spot you, making it easy to run around without being caught by pesky Bokogoblins.