Princes

Princes are children sent long ago to tiny planets called minor planets, tasked with awakening the magic of the crystals kept within them. Arco, the protagonist of the game, is the Prince of Wind.

Minor planets
Minor planets are characterized by their "reduced size, the Crystal altar and the frequent monster attacks" according to Mûn. Lily reveals that the monsters are born from the princes' magic in response to their fears.

The crystal core of a minor planet contains a unique magical element, which a prince can channel through the crystal heart they carry. A prince can choose to sacrifice himself and his planet to release the magic it contains, allowing Anks and other princes to channel it.

Arco starts to feel unwell if he's away from his minor planet Deiland for too long.

Corruption
The Dreamcatcher Spider can corrupt princes and destroy their planets by consuming their magical cores. She calls her corrupted princes Prince of Nothingness, regardless of their original element. Destroying their crystal heart frees them from the Spider's control, but presumably also cuts them off from their magic.

Known princes
There are seven known princes:
 * Arco, Prince of Wind on Deiland.
 * Demon Prince, Prince of Nothingness for the Dreamcatcher Spider. His original element is unknown.
 * Aki, Prince of Life on Alma. The Interstellar Patrol's classified information reveals that he sacrificed himself and and his minor planet at the age of 13 to release the element of Life.
 * When the Demon Prince is defeated, he mentions three princes who "released the magic of their planets" (including Aki), and three who "failed and [...] were overcome by the Spider" (including himself).