The Tempest Sons were formed during the 10th Founding, roughly 500.M35, in response to a growing number of Ork and Chaos incursions in the Scarus Sector. The exact date and nature of the founding is lost due to the ransacking of Prima Concordia's Librarium during the Siege of Ishkar and the incomplete records of the Adeptus Administratum, though it can be assumed that like their brothers founded during the Nova Terra Interregnum the High Lords of Terra deemed that the Scarus Sector needed its defenses bolstered during that era of conflict.