The Book of Lairs I & II. Did you use these handy books?
These accessories were released in 1986/1987 by TSR for AD&D 1E. They featured classic D&D monsters & the second added some Asian-themed monsters for OA.
Later books featured DragonLance, the Realms, Spelljammer & the Outer Planes. Each encounter provided stats & the lairs setup for the DM. Strangely, there were very few maps & the DM had to provide their own. These were great for wandering monsters & I used them extensively.
Michael Breault & Jim Ward authored the first. The cover of Book of Lairs I was done by Clyde Caldwell & originally graced the cover of Dragon Magazine #65. The Cover of Lairs II was by Jeff Easley
Are those guys attacking a gold dragon?
The second book was authored by David Cook, Jennell Jaquays, Anne Gray McCready, Bruce Nesmith, Jeff O'Hare, and Steve Perrin. Quite the lineup of authors for both books. Lots of great ideas & some neat monster combos.
https://etsy.com/listing/1401551125/the-book-of-lairs-tsr9177
https://etsy.com/listing/1387549224/ref4-the-book-of-lairs-tsr9177-vintage
@deidungeon inspired writing, never used.
@deidungeon I think I was still using them as recently as 2010. Like I always say, "I paid for all those rulebooks, so I'm going to use all those rulebooks!"
@contrarian That's our theory too, we're mostly playing 3.5 these days, but there are always AD&D, and Original D&D books close by.