The Grumani people were devout followers of the Children of Mani faith.
Grumani doctrine held that ethical behavior stemmed directly from the teachings of Mani, the religion's originator, as explained by Mani's Hierophants.
A religious division caused the Grumani to separate from the dissenting Spumani, sparking an eight-century long war between the two factions, which lasted until the Sith arrived in the Grumani sector during the time of the New Sith Wars. Eventually, the hostility between the two groups lessened and became simple dislike.