The Sword of Secrets is a revered artefact of the Dark Angels Space Marine Chapter. This sword is a master-crafted Power Sword of formidable potency created soon after the disappearance of Primarch Lion El'Jonson during the Fall of Caliban. It is the mightiest of the so-called Heavenfall Blades, the swords cut from a block of jet-black obsidian that struck the Dark Angels' mobile fortress-monastery known as the Rock whilst in orbit around the Feral World of Al Baradad. The blade of the Sword of Secrets is so incredibly well-crafted from a single block of the Heavenfall obsidian that it has not chipped nor lost its keen, razor-sharp edge over its many millennia of bloody use. This relic is borne by every successive Supreme Grand Master of the Dark Angels and is currently in the possession of Azrael. Only the Supreme Grand Master knows that it is also the only device that allows access to the deepest known dungeon in The Rock. Fitting the blade into a cleft in the wall unlocks the iron gate leading to a dark tunnel and the rune-protected cell in which the Arch-Heretic Luther is imprisoned.
- Codex: Dark Angels (6th Edition), pp. 52-53, 56, 58-59
- Codex: Dark Angels (4th Edition), pp. 42-45, 46
- Codex: Dark Angels (3rd Edition), pg. 18
- Codex: Angels of Death (2nd Edition), pp. 13, 41, 62
- Warlords of the Dark Millennium - Azrael, pp. 31-32