Honestly, it was the beautiful cover art by Liz Danforth that caught my eye since I'm a huge fan of her work, but after reading the book, I've had a lingering desire to adopt a few things from it to my D&D game.
M!M! is admittedly a fairly obscure title, even among old school players, so I'll give a thumbnail idea of what it's about.
The game is basically a variant of Tunnels & Trolls, the premise being that instead of playing brave heroes ridding dungeons and ruins of the monsters that live there, you are the monsters, ready and willing to ransack the towns, farms and other places the poor humans live. The game is fairly tongue in cheek and a fair bit silly, but there's some interesting bits here and there.
One of the ideas that struck me as useful is the inclusion of notes on the various monster types intended to make them more true to their mythological or literary source material. I've picked a few of my favorites and converted them to quick, unscientific D&D rules for use in a game.
Every dragon or dragon-type beast must have at least one soft spot somewhere on its external body. (Remember, Smaug, from The Hobbit, had that once scale missing on his breast.) Any dragon struck by a weapon on its soft spot dies.
The game goes on to explain that for every 100 weapons directed at the dragon, he must make a 'saving roll' to see if anyone in that mob hit his soft spot.
To adopt this to D&D without making dragons too easy to defeat, I suggest giving any character a 1% chance (a natural 01 result on a percentage dice roll) on their first, and only their first, successful attack on that dragon to hit his weak spot. Subsequent attacks do not get this chance, since once combat is in full swing, it is assumed that the dragon will protect his weak spot from hack and slashers. Optionally, a character who has researched or happened upon information that points out the possible weak spot (like Bard using Bilbos recon report to slay Smaug) may add 1 to 4 percentile points to the success range of that roll, either DM's caveat based on the quality of the information, or the result of a d4 roll, generating a 2% to 5% chance of success on that first attack roll.
If a successful attack roll is followed by a successful percent roll to hit the dragon's weak spot, the dragon must succeed on a Save vs. Death or be slain instantly. If the dragon makes the save, it still suffers maximum damage from the attack, negating the need for the attacker to roll for damage.
The Sphinx has a very high IQ, but is vulnerable to riddles, and will stop to engage in a riddling contest with any human or monster brave enough to attempt it. If the Sphinx loses, it must do the will (one time only) of whoever out-riddled it. If the Sphinx wins, the other is at its mercy.
There's not a lot of conversion needed here. If a Sphinx is encountered and combat has not begun, a PC may challenge it to a riddle contest. I strongly suggest playing the contest out through actual riddles between players and DM, but if you prefer, I'd roll 1d6 to see how many "rounds" the contest lasts, then having each side roll that number of either INT or WIS (player's choice) checks, keeping track of success (a d20 roll of equal to or less than the ability score being a success). The DM should do the same for the Sphinx, calculating its ability score as 1d4+14. The winner is the one with the most successes on the checks. In event of a tie, repeat for one more round of riddles. The winner is then owed a favor by the loser, as negotiated between DM and player, but as noted, Sphinxes are not merciful when they win, and their favor should be dangerous or otherwise annoying to the player.
Ghosts are non-material and are not vulnerable to material weapons. They are, however, susceptible to magic, and are likely to be magic users themselves. Humans who meet ghosts must make their saving roll to avoid panic , which reduces both IQ and Dex by half for the rest of the encounter.
This one could be fun and useful in illustrating fear when encountering the undead. Any time a character first encounters a specific type of undead of greater HD than their character level, they must make a save vs paralysis. Success on the saving throw means they grit their teeth and face their fear without any real hesitation, but failing the save results in panic, which results in a -4 penalty to all
die rolls until the undead creature is destroyed, turned or the character flees the encounter area for 1d4 rounds. Returning to fight that creature again requires another saving throw, as do future encounters with that type of undead until a success is rolled on the saving throw. Once the character has successfully overcome the fear of a certain type of undead, she can fight those creatures in the future without hesitation. I added the note about greater than the PCs hit dice to prevent 1st level PCs from freaking out and fleeing every time a skeleton or zombie shows up, we'll just assume they've heard enough horror stories and wife's tales that the minor undead, while repulsive, are no longer panic inducing to a fledgling adventurer.
That about wraps it up for the basic monster quirks stuff. Stay tuned next time for some bits regarding the "ecologies" and placement of some of the ubiquitous monsters of fantasy.
As always, please feel free to comment, including any similar quirks or house rules you use to spice up the monsters in your game.