Mert, whom many address more fondly as Papa Mert, is an alchemist of considerable esteem in the Undercity, a man of brusque manner and commanding presence who keeps his trade within a market quarter of the middling and better sort. He is curt and unwelcoming at the first meeting, yet he thawed toward Jean-Zera Mongé, who won him over by a respectful persistence — proof enough that beneath the gruffness lies knowledge worth the earning, offered only to those who trouble to earn his regard.
He serves the company at once as a contact and a resource, whether their want be of physic or of intelligence, and stands besides as a mentor to those who aspire to his art, Sidra al-Najjar among them. He will suffer others to watch him at his work, but under a strict rule of silence and with no hand laid to the business themselves — an instruction imparted, as it were, sidelong, that leaves his authority and his mastery quite undiminished and confirms his name as a knowing man in matters alchemical.
He is reckoned, too, an apothecary of parts, learned in the healing and the poisoning virtues alike of plants and fungi, and he teaches the safe gathering of them. He sets great store by a white powder he calls "Biyin," which draws the toxins out of the skin; when Sidra al-Najjar once brought him a fungus she had collected, he named it for the dangerous thing it was and would not rest until she had scoured her hands with Biyin, all the while instructing her in the plain properties of her samples.
Of late he showed the compounder's craft in full when Sidra al-Najjar sought his aid for a young tiefling wasting under the blood rot. Gruff as ever, he yet betrayed a buried compassion, hearing out her fears and undertaking to guide her through the making of a remedy; he furnished a thick paste of whitish-blue and explained that its use called for a ritual component besides, so joining the alchemical to the magical in his knowledge. He assisted her at the application, laying bare the afflicted places and overseeing the rite, and afterward thanked her for her help — confessing, with some candour, that it was the first time he had put the technique to practical use — before taking his leave for home.
Beyond his alchemy, Papa Mert is a fixer of local standing, one who will find a man temporary lodging and a helping hand at need; he keeps a disguise kit and will share a cloak, and is nothing if not resourceful. Familiar with the Undercity and all who dwell in it, he is wont to question newcomers as to their wants and their intentions before offering them shelter for three days — a small measure of the trust he extends to those he chooses to aid. He has had his part in the logistics of the party's undertakings, seeing them safely housed to regroup and lay their plans; and his presence lends the Undercity one more distinct character, a man whose commanding temper ensures that any who would learn from him must first respect his methods and keep the silence he demands.