White Temple is a stage in The King of Stories. It is not from any particular universe in the game. Peach and Purin are playable in this stage.
White Temple is an ancient, white city made of ruins, surrounded by beautiful fountains and waterfalls, as well as vegetation. A very similar stage called Lequidora Water Palace in The Chronicles of Sonic the Hedgehog: Rise of the Heroes can be considered an influence to this stage.