While Mercurio was adept at the Cappadocian study of the death, he also proved to be ambitious and untrustworthy, plotting to kill Garinol and usurp his power.
Mercurio was a Kabbalist, and Garinol intended to use Mercurio's knowledge to gain knowledge of the Golem of Prague. Mercurio was charged with keeping the safety of the Cappadocian haven under Petrin Hill Monastery, but knowing that he would no longer be needed if Garinol unlocked the secrets of the Golem, he afflicted it with Grave Rot.
Garinol was suspicious of Mercurio, particularly when Mercurio sealed off his private crypt so that Garinol could not enter. (Although Garinol could have broken the seal with his Anointed Skull of the Lamia, he declined to do so because he still needed Mercurio's rare knowledge.) In order to distract Garinol from his own plot, he tried to turn Garinol's Brujah allies against him by stealing a valuable fragment of the Book of Nod from Ecaterina the Wise.
His treachery was exposed when two Brujah, Wilhem Streicher and Christof Romuald, infiltrated the haven while Garinol was absent. Mercurio was slain, his plot against Garinol exposed, and the Nod fragment recovered.