My particular discipline is that of Materia Medica, for human medicine was my original calling. Our understanding of our own vital mechanisms is vast and admirable, but we can never know too much about our own biology and how to protect, repair and improve it. It is our burden as a species to exist in a galaxy riven by war, and where war goes, so flourish its hand-servants, injury and disease. It may be said that as each war front advances, so medical knowledge advances too. And where armies fall back in defeat or are destroyed, so medical knowledge retreats or is forgotten. Such are the lapses I seek to redress.

Upon that very purpose, I came to Symbal Iota late in my forty-eighth year, looking for Ebhoe. To provide context, let me say that this would be the third year of the Genovingian Campaign in the Obscura Segmentum, and about nine sidereal months after the first outbreak of Uhlren’s Pox among the Guard legions stationed on Genovingia itself. Also known, colloquially, as blood-froth, Uhlren’s Pox was named after the first victim it took, a colour-sergeant called Gustaf Uhlren, of the 15th Mordian, if memory serves me. And I pride myself it does.

As a student of Imperial history, and Materia Medica too, you will have Uhlren’s Pox in your memory. A canker of body and vitality, virulently contagious, it corrupts from within, thickening circulatory fluids and wasting marrow, while embellishing the victim’s skin with foul cysts and buboes. The cycle between infection and death is at most four days. In the later stages, organs rupture, blood emulsifies and bubbles through the pores of the skin, and the victim becomes violently delusional. Some have even conjectured that by this phase, the soul itself has been corroded away. Death is inescapable in almost every case.

It appeared without warning on Genovingia, and within a month, the Medicae Regimentalis were recording twenty death notices a day. No drug or procedure could be found that began to even slow its effects. No origin for the infection could be located. Worst of all, despite increasingly vigorous programmes of quarantine and cleansing, no method could be found to prevent wholesale contagion. No plague carriers, or means of transmission, were identifiable.