Certainly at least one of you in the literary crowd has picked out the esteemed H.P. Lovecraft's "The Alchemist" as the source for this arc. The relevant text posted below:
"One night the castle on the hill was thrown into the wildest confusion by the vanishment of young Godfrey, son to Henri, the Count. A searching party, headed by the frantic father, invaded the cottage of the sorcerers and there came upon old Michel Mauvais, busy over a huge and violently boiling cauldron. Without certain cause, in the ungoverned madness of fury and despair, the Count laid hands on the aged wizard, and ere he released his murderous hold, his victim was no more. Meanwhile, joyful servants were proclaiming the finding of young Godfrey in a distant and unused chamber of the great edifice, telling too late that poor Michel had been killed in vain. As the Count and his associates turned away from the lowly abode of the alchemist, the form of Charles Le Sorcier appeared through the trees. The excited chatter of the menials standing about told him what had occurred, yet he seemed at first unmoved at his father's fate. Then, slowly advancing to meet the Count, he pronounced in dull yet terrible accents the curse that ever afterward haunted the house of C-.
'May ne'er a noble of thy murd'rous line
Survive to reach a greater age than thine!'
spake he, when, suddenly leaping backwards into the black woods, he drew from his tunic a phial of colourless liquid which he threw into the face of his father's slayer as he disappeared behind the inky curtain of the night. The Count died without utterance, and was buried the next day, but little more than two and thirty years from the hour of his birth. No trace of the assassin could be found, though relentless bands of peasants scoured the neighboring woods and the meadowland around the hill."
While the fatal age here is thirty-two, whether Onstad's twenty-six has any significance is yet to be determined. Also, I'm really looking forward to see how the thrillingly over-the-top climax of "The Alchemist" recurs in the Achewood variation.