Cayr Ulios was the central safehold of the Wilt Leaf elves at the plane of Shadowmoor. It is possible, but not certain, that Cayr Ulios was the product of Great Aurora transformation of the Gilt Leaf capital Lys Alana. Cayr Ulios was the seat of Wilt Leaf king and queen.
The safehold became the focal point in the last days of the battle between Oona and Maralen. Similarly to Kinscaer, Oona contracted the elves' help and then killed all of the denizens by her thornvines, in order to feed on their magical abilities and life force. Cayr Ulios was the place of the last great battle of fae, where Maralen's rebels and Oona's loyalists clashed against each other. In the final moments of the war, Wilt Leaf First Vigilant Gryffid sacrificed himself to sever the connection between Oona and the King and Queen, who were serving as an unwilling conduct for the elven life energy that Oona drew on, significantly weakening her before her last showdown in Glen Elendra. Cayr Ulios was later repopulated by Wilt Leaf survivors and possibly other elves.