Warlock! Corrupted (2020)

From publisher blurb:

Lure of the Dark

Some magicians delve too deeply into the ways of other worlds, other existences. They seek to learn all that the cosmos has to offer, and wish to understand the very nature of creation. Much of this research starts out innocently enough, but in the quest for ever greater knowledge, these wizards are drawn to older sources and texts best left unread. Eventually, no matter the nobility of the goal, such research inevitably ends with demonic contact.

Beyond the mortal worlds, there are all manner of beings more ancient that all the empires of man, elf, dwarf or halfling, and most are eager to talk to any that will listen. Magicians know the traps these beings set, and guard themselves well against the snares of demonkind. Nevertheless, such is the hubris of the mighty - in the end; all succumb to the promises of demons. Treading down dark paths, these magicians slowly change to become pawns of demon kind, wreaking havoc on the Kingdom. In the hushed circles where such things are discussed, these magicians are referred to as 'the corrupted'.

This supplement outlines the corrupted, their nature, goals and powers, to allow the games master to incorporate these desperate lunatics into their campaigns.