Kryptos (The Horus Heresy Short Story)

Bloodied but unbowed, the Raven Guard and the Iron Hands fight on. In the wake of the Dropsite Massacre, the shattered Legions are still prepared to bring the fight to Warmaster Horus and his traitorous allies. On the doomed forge world of Cavor Sarta, two veteran warriors of the Imperium strike deep into the heart of Dark Mechanicum territory. With bolter and blade ready to cut down any who cross their path, they will seek out the enemy's most valued the mysterious Kryptos. Read it because
The mysterious Kryptos appears in other tales, and this is your chance to find out just how the brave warriors of the Shattered Legions came to use it… and the price they paid.