The Lions Defiant are a Loyalist Codex Astartes-compliant Space Marine Chapter of unknown Founding and origin. Almost nothing is known about this Chapter in Imperial records. In 992999.M41, a massive event known as the Night of a Thousand Rebellions occurred. Uprisings and discord struck countless planets across the Imperium. Unrest raced like wildfire, consuming many outlying planets, but also supposedly secure worlds like Enceladus, Darkhold, and Minisotira. Contact was lost with large swathes of Segmentum Pacificus. Even the homeworld of the Lions Defiant Space Marine Chapter was lost to the anarchy caused by the coordinated activity of secret cults and frenetic agitators.