Wilderlands Age of Worms
Bozal Zahol was a middle-aged tiefling with a flaccid and misshapen figure. His fiendish ancestry was evident in the unnaturally green, almost fluorescent color of his eyes, his twitching tail, the vestigial horns on his brow, and his hoofed feet. The party encountered him in a secret section of rooms hidden beneath the Arena in Tula. He was an extra creepy dude, specializing in summoning unnatural creatures from Beyond the Void. The party never found that out, though. They finished him off before he got a chance to summon any. They did, however, determine that he was responsible for using the Apostolic Scrolls to summon the Apostle of Yog, an extra-powerful ulgurstasta. The party took care of that, though.
I made Bozal an Archivist/Alienist, instead of a regular cleric, because I thought it would make him both scarier and tougher. It achieved neither. Anmor did get a nice extra prayerbook out of the deal, though.