The Henderson Monster Creation Table

Steve Henderson, (1944-2006) of Gloriantha, RuneQuest, Chaosium, DunDraCon, and Society for Creative Anachronism fame, crafted a nice little random monster generator for Jeff Pimper's and Steve Perrin's first All the World's Monsters (1977) tome. (You can still purchase a PDF of the book here from Chaosium. 256 critters only $5!)

The tables by themselves will produce some tough nasties. Ha, there is no procedure for mitigating a creature based on the party's capabilities. That's some old school, you gots to know when to beat the expeditious retreat.

There are also percentile chance for "special" movement, attack, and other abilities. Also it seems each beastie gets at least one special detection and immunity.

Interesting bonus, you make up the creature's appearance however you wish. The only visual cue is whether the monster is "Indescribable," "Hideous," "Average," or "Beautiful."