As a warning, along with sporadic library reserves, I found a bunch of old RPG novels among the remnants of mom's house, then found a few other volumes on used book sites, so expect some really odd entries over time.
Today was King of the Dead by Gene De Weese, which is more or less the origin of Azalin, who's later stories are found in Lord of the Necropolis. (If you click that link, there's an awesome picture attached to the post.) For those not versed in such esoterica, Azalin is a lich who rules the Ravenloft Domain of Darkon, and is pretty much the arch nemesis of Strahd, the Vampire Lord around whom the entire setting is based. Firan, as he was known as a human, started in Oerth, aka the Greyhawk setting, middle son of a King who thoughts magic users were evil. So, because of course he does, Firan learns the arcane arts, manages to get his younger brother possessed, then runs off to follow his mentor somewhere outKingdom.
He learns tricks to siphon off the life force of those he kills, and becomes king after his eldest brother dies. Firan rules by executing anyone who breaks his laws. He marries, finds out the wife cursed him, erases the curse, and she bears him a son. Irik, named after his possessed younger brother, ends up commiting treason against daddy dearest, since he doesn't agree with Firan's policies. Firan beheads Irik, and then regrets it, thinking he should raise his son and teach him to be more like his father. Well, that doesn't quite go as planned, and Firan starts hearing taunting voices of those he cared about, which in turn leads him to turn himself into a lich. (An observation: most of the art depicting Azalin makes him look a bit like Skeletor right before He-Man kicks his ass.)
So, Firan eventually gets sucked into the mists and winds up in Barovia. He refers to himself by his old title on Oerth (Aza'Lin), which the Barovians take to be his name. We get a short chapter on his working with and against Strahd, before Azalin enters the mists again, and eventually becomes the leader of his own Dark Domain, and his punishments of never being able to learn new magic, and finding the only way he could fully resurrect his son is to torment himself. Or, he could forgive himself, but that would mean him admitting he was wrong.
It's fun, and frankly, Azalin more than Strahd understand the nature of the realm and its torments. He's probably the only Darklord who understands how to end his imprisonment, but is too stubborn to do so.
It's a tad silly in places, but it's a fun read none the less.