Esterhazy was the armorer and swordsmith in the town of Fano and renowned for his work; so much so that he always had on him a bone whistle that, when used, signaled to hidden bodyguards that he was in trouble.
In the fall of 1267, he was informed by Nycklar that Leo Bonhart was on his way to outfit a captured Ciri (under the alias Falka) with a sword to then have her fight for Claremont's entertainment. While Esterhazy originally had some swords ready to go, they proved unsatisfactory. However, on see that Ciri was no ordinary fighter, he brought out one of his prized swords available: Zireael, an original gnomish gwyhyr. While the sword was very expensive, he gave it as a gift to Ciri "so that what is to come about, will come about."
Several days later he was visited by a faction of Stefan Skellen's gang to learn what transpired between him and Bonhart. Esterhazy proved to be stubborn though, only revealing that Bonhart had dropped in and moved to use his whistle, but before he could one of the members, Joanna Selborne, was a psionic and used her abilities to stop him before getting him to reveal everything that pertained to the bounty hunter.