Every Ben's Knife is engraved with a number corresponding to when it was made in relation to the other knives. The form of the blade apparently makes it possible to recognize some of its properties (such as toxicity), while the sharpness may indicate in which period of the blacksmith's activity the knife was forged.
There are 288 different Ben's Knives in total. The serial killer and blacksmith Benny Delon forged a unique knife for each victim he killed, showing that he had 288 victims. He put the knives up for sale in his storefront alongside his regular swords and other ordinary knives.
Ben's Knives are known to be exceptionally sharp, enough to cut Silva Zoldyck's tough skin. At least one of them is imbued with a toxin so powerful that 0.1 mg of it could paralyze a whale. The aura of their forger remains in them after about a century from his death.
Yorknew City arc
Gon and Killua discovered that these knives can be found by using Gyo to detect the aura Benny Delon unintentionally left on them. At the present time, the prices of the Ben's Knives vary depending on the incised numbers, but each of them can be sold for at least 5 million.
- According to Killua Zoldyck, his father—Silva Zoldyck—likes Benny Delon and his works.