Of Xorn and Gorgons...
I have a monster problem. Namely, I really love monsters. It is a weakness of mine for role-playing games. I know I can make my own in a pinch, but sometimes the flavor text or concept of a monster gives me something cool to work with.I will ignore almost any other source book of role-playing game puts out, but I simply cannot resist a good selection of monsters. Even when I gave way most of my D&D 3E and Pathfinder 1e material, I held on to the bestiaries.
Unfortunately, Pathfinder bestiaries and the 5th edition Monster Manual and Volo's Guide to Monsters don't help me much now that I've moved back to OSR games, I don't really have a good monster book in hardcopy.
Basic Fantasy RPG has a great monster selection. So does Swords & Wizardry. And Low-Fantasy Gaming, with a little conversion. But they are all sections of a larger book. And sometimes flipping through to find what I'm looking for can be a little time consuming. They also both have some issues. Swords & Wizardry does not present a morale rating for monsters, for example. Basic Fantasy RPG has almost (but not quite-, nor consistently+) doubled the XP value of the monsters that are in the book, as Basic Fantasy relies more on combat and less on treasure.
And while I hate to say it, well the rules cyclopedia is the most comprehensive versions of Dungeons & Dragons around, it's selection of monsters is lackluster.. I have always felt that that was one of the greatest weaknesses of the Cyclopedia.
But, I do need something. I keep planning for monsters that I don't have the books for. Last night I planned encounters with Gorgons and Xorn, and discovered to my dismay I had statistics for neither in a format compatible with the game I was playing. I covered by opening up a website where I knew someone had copied the entire AD&D2e Monster Compendium, and thankfully my players didn't wander off that way anyway.