Festus was a healer once, and by every account a brilliant one. When plague swallowed his city he worked himself to ruin, prayed to every god of hearth and healing, and was answered by none of them — until, in the grey hour when his hope finally broke, something vast and grandfatherly cleared its throat. Nurgle offered exactly what Festus had begged for: an end to his patients' suffering. He has spent every day since honouring the letter of that bargain.
The Leechlord shambles through the realms as a walking apothecarium, flesh hung with fattened leeches, back racked with clinking flasks, brewing new blights with the tenderness other men reserve for children. The obscenity of Festus is that the healer never died. He takes pulses. He mops brows. He speaks softly to the dying while dosing them with something new, because in his rearranged heart he is still curing people — hope being the disease, and despair merely a symptom of incomplete treatment.
His great work goes on in laboratory-gardens seeded across the realms, and nowhere dreads it more than Ghyran, whose stubborn vitality he treats as the most fascinating of chronic conditions. Festus is chasing a masterpiece: one final elixir to cure the realms of mortality itself. The worst of it, survivors whisper, is that under his care the pain really does stop.