EX Trial of the Sword

EX Trial of the Sword is a sub quest added to Breath of the Wild DLC 1. Initially it bestowed upon the player by a "mysterious voice". Obtaininng the quest also unlocks the EX Strange Mask Rumorrs, EX Teleportationn RUmors! and the four Misko's Treasures (EX Treasure) sub quests.

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You hear a mysterious voice that mentioned something about a glorious trial...

What could this trial be? The voice instructed you to speak with the Great Deku Tree at Korok Forest to take on the challenge...