Sigismund is the name of the boy that the Adeptus Sororitas guarded so diligently in their fortress on Zephyr. Found in the wilderness several years prior by a childless couple he remembered nothing of his early years - save his name. He was adopted into the local community, but quickly attracted the attention of the Sisters when rumours of his intelligence, charm, and physical perfection reached the ears of High Palatine Salt. The Sisters studied him very closely indeed, for he proved quite unlike any other man they had encountered. Eventually the decision was made to dispatch him to the Adeptus Terra, but because of the Reaving of Finial, Kull raiders, and the general chaos of the Segmentum Solar the transport mission was aborted several times.

When the 10th finally breached the Sisters' fortress after nearly a year of combat and siegecraft Captain Anaximander (in the guise of a sergeant of the Tigers Argent) prevented the elimination of the boy. When faced with Castor the boy seemed both unafraid and open-minded. Very unlike most Imperials. The boy's blood proved extremely potent and Castor decided to go to Segmentum Tempestus to present him to the Primarch. He suspected the boy might be the reincarnation of the Black Templar's legendary founder by the same name. Based upon this assumption Castor decided to go ahead and turn him into an Astartes. Over the course of the 6-month journey the boy grew at an unprecedented rate. He also proved and apt an willing pupil, absorbing ever scrap of the Word presented to him. His mind was undeniably a religious one. He would sometimes question the Word or add to it, pointing out that faith was always changing. Even Lorgar had reinvented himself once - and adjusted his teachings multiple times after that.

Lorgar more or less confirmed the boy's pedigree, but noted that he might in fact be one of the lost Primarchs instead. He could not tell for certain. He then dismissed the boy as unimportant, for his eyes are fixed on the grand prize - the reincarnated Emperor - and he has no time for lesser creatures. He bade Castor take care of the boy and his education, indicating he had great confidence his Apostle.

On the way back to Calixis Castor had Anaximander train the boy in combat and warcraft. Aagin he proved a most apt student, easily picking up the skills of a full Astartes in less than half a year. In all he's as fine a Space Marine as you can hope for, fearless and with peerless combat skills. He also has the fire and the faith. Men follow him easily.

The question is, what are you going to do with this Sigismund?