One of the most elusive figures in Yharnam is Izzy. The man made hunting tools and employed a weapon, implying that he was a hunter. However, such tools were derived from the body parts of darkbeasts, including his weapon of choice the Beast Claw. The nature of these inventions reflect a desire to be more like his prey, which is reasonable given the raw power and extraordinary vitality of those more horrifying beasts. If only hunters could spill blood with a mere swipe of their hands, knock back swarms with a simple howl of their voice; then, they too could truly match those monstrosities. Moreover, getting in touch with man’s more primal side provides a greater high than even blood treatment. This seems to be the motivation for taking his kills and constructing tools for he and other hunters to handle, though we can only acquire the one found in the woodland village outside of Yharnam — presumably the developers’ callback to an earlier iteration of the character, who is framed as a Yharnamite with a surprising bias for outsiders in cut dialogue. Izzy reveled in the hunt of beasts, in both senses.
One of the forbidden hunting tools made by the apostate Izzy’s hands.
It is a catalyst that very temporarily borrows the power of the abominable undead black-beasts and should send those in the surroundings flying from the forceful beast roar.
That piercing scream is nevertheless something produced with the user’s vocal cords. Who in the world lies within man?
Beast weapon used by the apostate Izzy.
This weapon, which took, whittled, and bound an abominable undead black-beast’s long bones, is still alive and temporarily guides the user to a beast nature by unleashing.
The beast nature is boosted by the torn flesh and spurts of blood from attacks, and continuing them will also bring the user further power and pleasure.
However, this is precisely why he has been labeled an “apostate”, (背教者) literally one who defies the teachings of the faith; in this case, the Healing Church. The clergy warned against the lure of beasthood, yet Izzy still wanted to be closer. This suggests that he wasn’t a church hunter, more likely originating out of the old workshop — though whether that remained the case is another matter. Aside from being personally denounced, the apostate’s tools were deemed forbidden, and so it is possible that he was driven out from hunter society. Of course, it is also possible that this all occurred postmortem. After all, neither item description mentioning him indicates his current state, so he may well be long dead by this point. And although we have no body to confirm, we are provided some hint to his cause of death.
We can summon Beastclaw Josef in the Loran Chalice Dungeons, so named for his use of Izzy’s favorite weapon. Whether aware of Izzy or not, the charred hunter of Gehrmans’s workshop has apparently followed the apostate’s path approaching the beast within. “Followed” is especially apt to say considering that we can encounter an enemy hunter identical to Josef in Loran as well, dubbed instead Izzy’s Admirer — or more accurately, “Izzy’s Successor”. (イジーの後継) Clearly, the Josef we summon across time and space to help hunt the threats in the dungeon became consumed by his beastly nature as he fed that bloodlust, ultimately turning hostile to even his fellow hunter. And if he is succeeding Izzy, then we can presume that the apostate met with the same fate. In that case, there is little chance he wasn’t hunted like any other mad beast terrorizing the streets of Yharnam. We may even get the chance to see his sorry state, in fact.

In exploring the Hunter’s Nightmare, we inevitably come across a bestial man wearing nothing but old hunter trousers. Based on his form, this old hunter tapped into the Beast’s Embrace, yet this rune was discovered as part of the Healing Church’s secret experiments and ultimately forbidden, so we can only assume that this revelation came to him independently. Indeed, he wields the claw showing prior interest in nearing beasthood despite carrying the badge of the Oto Workshop — apparently always the nonconformist. The description makes no mention of Izzy crafting this weapon for hunters in general, with Josef’s only reason for diving down to Loran seemingly being to acquire his. Therefore, it is more likely that the topside claw wielder is the actual apostate. Some might argue that this hunter doesn’t utilize Izzy’s only other acquirable invention, Beast Roar, but this can be credited to his transformation, which has its own kind of howl. And regardless, it is to be expected that his hell after death be reliving those moments of insanity chasing a beast’s hunt.