Sorry for the lack of posts of late. School gave us a 4 day weekend and I've been getting caught up on grading tests and lab reports as well as doing some reading, organizing that wreck of a man cave I have, and just resting. One of the things I came across was an old photocopy of a monster stat block and description. The creature was used by the guy who taught me D&D way back in 1978. (Thanks, Grant!) He said this was the creation of one of his frat brothers at Rose-Hulman. So, if you recognize this, let me know so I can properly credit you. Below is my best transcription of the page.
Number Appearing: 1-2 (75%), 1-20 (15%), 2-40 (5%), 3-60 (3%), 5-100 (1%), 20-400 (1%)
Armor Class: 6+dexterity
Hit Dice: 4
% in Lair: 40%
Treasure Type: Qx5; G, W; U
# of Attacks: 2 or 1
Damage/Attack: 1-8, 1-8, or by weapon type
Special Attacks: Cause Depression, Curse (leaders only)
Special Defenses: +1 or better weapon to hit
Magic Resistance: 10%
Alignment: Chaotic-Depressed (Neutral)
Size: 4 1/2' - 5 1/2'
Grumble Beasts appear as pudgy, hairless gorillas with grey skin. They travel about looking for Luck Stones to give to their leaders. They were cursed long ago by a high level cleric or a god for some offense and the curse has affected the whole species. All but the "priests" are cursed with bad luck and continual depression. Each Grumble Beast has the ability to Cause Depression (save vs. Spells) in any individual. Killing a Grumble Beast will transact its curse to its killer (save vs. Magic) with 1-3 days, save for half time.
Leader types: "Priests" are good luck charms. All Grumble Beasts within sight of a priest will have the curse temporarily negated. Killer of a priest gains the enmity and curse of the entire tribe for as long as they live. If the tribe is killed, same as above applies.
For every 10, the "priest" is a 1st level Cleric and the chief has 5 HD with AC 5.
For every 20, the "priest" is a 2nd level Cleric and the chief has 6 HD with AC4.
For every 40, the "priest" is a 3rd level Cleric and the chief has 7 HD with AC 3.
For every 100, the "priest" is a 3rd level Cleric and the chief has 7 HD with AC 0 and +2 or better weapon to hit.
King of the Grumble Beasts has 10 HD, AC -2, and is Chief Priest (5th level Cleric). Only +3 weapons or better will hit.
Every 50 years, all Grumble Beasts attend a large gathering. If encountered in numbers greater than 50, the tribe is in exodus for 1-4 years to a new land.