Rosalina is a recurring character that debuted in Super Mario Galaxy, first appearing in the Gateway Galaxy. She is a very powerful figure, as her duty is to watch over and protect the cosmos, while also serving as the adopted mother of the Lumas and commanding the Comet Observatory. Rosalina's backstory is chronicled in her storybook told by her in the Comet Observatory's Library in Super Mario Galaxy. Nine chapters are unlocked throughout the game, and the last is unlocked by completing the game. The above text is from the Super Mario Wiki and is available under a Creative Commons license. Attribution must be provided through a list of authors or a link back to the original article. Source: https://www.mariowiki.com/Rosalina