Spoiler warning: Plot or ending details follow.
- "When the moon bleeds and the fiends are reborn
The monks will invite you as they have sworn.
But first you must stand on the pedestal bare
With nothing between you and the night air." - — Kass
Under a Red Moon is a Shrine quest in The Legend of Zelda: Breath of the Wild. It is obtained from the Rito minstrel Kass at Washa's Bluff south of Hyrule Ridge. He recites a song as a hint to find a nearby Shrine. To complete the quest, Link must stand on a nearby Ancient pedestal during a Blood Moon wearing no armor. Once this is done, a shrine will emerge from the ground nearby.
Spoiler warning: Spoilers end here.