On my lunch-break today I walked up the street to find a mailbox to drop a letter into. On my way back to my office-building, I noticed an abandoned paperback book on the sidewalk, and quickly scooped it up. What I saw on the cover was quite heartening:
Oh man, 1940s pulp sci-fi! With giant white-furred gorillas! I haven't begun reading it yet but just based on the cover I want to make a monster. For your AD&D/Labyrinth Lord/other OSR ruleset of choice, I present...
No. Occurring: 1d4 (2d4)
Movement: 90' (30')
Armor Class: 5
Hit Dice: 8
Attacks: 2 (claw or weapon/bite)
Damage: 2d8 or as weapon/Disenchantment (see below)
Outlaw Apes are giant (15'+ standing on their hind legs) white-furred gorillas, more intelligent than their ordinary kin though still animals, and incapable of comprehending the principles of Law or Chaos, Good or Evil. Despite their great bulk, they can Move Silently and Hide in Shadows as a Thief of 8th level, and can perform Backstabs. While Outlaw Apes commonly rend their foes with teeth and claws, some (particularly those who have observed adventurers before) have begun crafting large, crude weapons. These count as a short sword or light warhammer to the Ape, but as a greatsword or sledge hammer to a human that loots one of these brutal weapons.
More concerning, Outlaw Apes feed on magical energy. They are especially drawn to the auras surrounding magical items, and will attempt to steal and swallow whole small items such as amulets or rings, or chew the magic out of larger items such as enchanted weapons or armor. On a successful bite attack, the Outlaw Ape can attempt to consume some of the enchantment on these items. The item has a 10% chance per +1 of enchantment to resist being consumed; as such, a +2 longsword has a 20% chance of resisting the bite; if it fails, it becomes a +1 longsword with a 10% chance of surviving the next bite.