Rare Treasure could be obtained from the Treasure Trove event.
A brown treasure chest with ornate gold trim and pink gems inside it.
The other parts of this suit are Figure in Mist, Soft Heartbeat, Jingling Jade, Dreamy Reality, Rose Dream, Maze of Mist, Elegance Everywhere, Eternal Flame, Window of Time, Velvet Dreamland, Red Heart Crown, Illusion and Reality, Samsara Mirror, Rose on Palm, Spring of Inspiration and Mischievous Elf.
There is an alternative version of the suit. It contains Figure in Mist, Rose Palace, Eternal Flame, Window of Time, Rare Treasure, Velvet Dreamland, Red Heart Crown, Illusion and Reality and Mischievous Elf.