A group of three Royal Dancers appear as floor guardians of the 201st floor of Tartarus. They block Fear and Rage, but are neutral to all other status effects.
The trio of Royal Dancers have a lot of ailment moves in their arsenal to make the fight against them extremely tedious. Between Poisma, Pulinpa, Marin Karin and their group-affecting versions, it's very difficult to go through the fight without at least one party member being afflicted. However, between these three ailments, Poison is the most benign as it doesn't restrict control of your party. While the Dancers have threatening attacks like Primal Force and Heat Wave, they also tend to waste their turns futilely casting ailment skills (since those will fail on party members who already have an ailment). Having Yukari Takeba around is a must since she can cure Charm and Panic easily, but be careful if she gets Charmed herself.
The Dancers are vulnerable to ailments (barring Fear and Rage), but they have ailment-curing moves to make this a futile endeavour unless you affect all three at once. That said, if you can repeatedly inflict those ailments you can force the Dancers into wasting turns curing each other. For best effect, turn their tactics on them by inflicting Charm on all of them with Dreamfest or a Sexy Dance augmented by Charm Boost. Hitting them with Panic through a Tentarafoo is also effective as it leaves them only with their normal attack to threaten your party.
Royal Dancer later reappears as a normal enemy in the Adamah Block of Tartarus between floors 229 and 235. In The Answer, it will appear as a red Shadow in the first section of Caina within the Abyss of Time.
In Golden, it may appear on B1F to B4F. It may also drop Milky Quartz for trade at Shiroku Pub. Selling six Yellow Cords is enough to unlock the Wooden Ebisu in the shop.