Powers and abilities
Tiara can take the form of different hats, including Peach's Tiara.
Above Peach's castle
During the events "in the skies above Peach's castle", Bowser kidnapped Princess Peach and Tiara on his airship. While Bowser proposed a forced wedding to Peach, he used Tiara as Peach's headdress.
While Peach, Bowser and other attendees were present in the wedding, Mario and Cappy interrupted the wedding. After Mario fought Bowser, Mario, Cappy, Peach and Tiara reunited. They escape from the collapsing area to the moon with Mario and Cappy possessing Bowser. Meanwhile, Mario and Bowser proposed to Peach, but she rejected them and left with Cappy and Tiara to the Odyssey. Mario jumped onto the Odyssey with Bowser stuck on the moon.
Peach and Tiara travelled around the kingdoms in Peach's "own terms" while collecting Power Moons. Mario visited them and Peach gave Power Moons to Mario. After visiting many kingdoms, Peach and Tiara return to the Mushroom Kingdom.