Herexen
Image © Paizo Publishing, accessed at Archives of Nethys here
[As part of PF2e's divesting from the OGL, a number of classic monsters inherited from the 3e Monster Manual and the Tome of Horrors have undergone some branding changes. Ankhegs are ankhravs, treants are arboreals, kytons are velstracs. And huecuvas are now herexens. The name "huecuva" was taken from Mapuche mythology, but the actual entity has nothing to do with undead clerics. And the mechanics of the D&D/PF1e huecuva are a remnant of a Gygaxian-era gotcha encounter--what looked like a kindly cleric infected you with disease by touch--and is weirdly low-intelligence. So I welcome this change to both name and mechanics wholeheartedly.]
Herexen CR 2 NE Undead This person is clearly dead, with rotting skin and half-missing facial features. It wears a holy symbol around its neck, but its talisman has been clearly defaced.
When a cleric forsakes their god before dying, their body may rise again as an undead heretic known as a herexen. Herexens hate the god they once worshipped, and go out of their way to desecrate holy spaces, interrupt festivals and slay adherents of the faith. They may attract necromancers or death cultists with their activities, and some even continue to advance as clerics, albeit turning to the worship of some demon lord, god of undeath or similar fell power. Herexens may be found as lone predators, or gathered together into parodies of worshipful congregations. In numbers, herexens often engage in cruel parodies of liturgical ceremonies.
A herexen focuses its attacks on divine spellcasters, especially those that worship the god that they once did. A formerly sacred weapon in their hands becomes a tool against all servants of the divine. Herexens are capable of using some clerical magic, thematically similar to that of the god they once followed. They can also inflict negative energy with a touch, which they use to both harm others and to heal themselves or any undead they may have allied with. When slain, a herexen explodes in a burst of negative energy.