*{{Main|Battle of Signus Prime}}

During the [[Horus Heresy]], Signus Prime was the site of an important battle between the Blood Angels and the daemonic armies of [[Ka'Bandha]].{{Fn|1}} After the battle, the entire cluster was declared ''morti perpetua'' ("forever dead") and quarantined. The Blood Angels expunged all records of their presence on Signus, resettled the few living survivors in neighbouring systems, and deployed beacons to warn starfarers away from the Signus system.{{Fn|2}} They also deployed a tactical cyclonic device to destroy the Cathedral of the Mark and a massive chunk of the continent with it.{{Fn|3}}

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