The Trial of Monsters
The quest is located at the icon of Monk Maz Koshia, found just north of Gerudo Town. This quest is unlocked after completing the Destroy the Yiga Clan! Chapter 4 scenario. This quest must be completed alongside The Trial of Stones and The Trial of the Mighty Foe, as part of the Trial of Monk Maz Koshia. Completing all three will unlock the Trial of the Ancients.
"As words written in light appear before your eyes, a voice from nowhere relates the same: "Only those who pass through the door of the Trial of Monsters may seek our power.""
"When you offered the materials, the words of light changed. The voice said, "You have done well to pass through the door of the Trials of Monsters. Now we grant you part of our power.""
- Qualify for the Trial of Monk Maz Koshia