The heroes of light are four heroes that were seen in the book of the Light Prognisticus, which were meant to defeat the Dark Prognisticus. Mario is the first of the heroes, followed by Princess Peach, Bowser, and Luigi. In the end of the game, they prevent the end of all worlds.
It’s known each hero of light plays a different role in the legends
1 : the Man in Red will destroy the Chaos Heart using the Purity Heart
2 : the Fine Maiden and the Dark King will marry creating an unstable power that recreates the Chaos Heart
3 : the Man in Green will be the reincarnation of the Great Grandpa of Count Bleck thus he will be the ideal host of the chaos heart and its power expands possibly tenfold when he is its host he also will be the judge of which prognosticus will be correct whether it’s the Light or the Dark thus being more neutral than the other heroes