During the Main Story, Mario and Cappy will have to find Power Moons in order to power up the Odyssey to travel from kingdom to kingdom. After the Main Story is completed, Mario can find and obtain additional Power Moons in order to unlock new Kingdoms and Costumes. In Ruined Kingdom, there are 5 Power Moons that Mario can find during the Main Story. Some of these Power Moons will not be able to be found and obtained when first entering the kingdom; some Power Moons can only be obtained (even if listed below) after the main objectives have been completed in Ruined Kingdom. (Even more will appear after the Main Story is completed.)
Ruined Kingdom Power Moons & Mission Titles (Main Story)
Ruined Kingdom Power Moon 01 - Battle with the Lord of Lightning!
Ruined Kingdom Power Moon 02 - In the Ancient Treasure Chest
Ruined Kingdom Power Moon 03 - Roulette Tower: Climbed
Ruined Kingdom Power Moon 04 - Roulette Tower: Stopped
Ruined Kingdom Power Moon 05 - Peach In Ruined Kingdom
Additionally, there will be 5 Post Game Power Moons that can be found and obtained in Ruined Kingdom.