Here's one I've been wanting to tackle for awhile.
This is from the Demon Generation article.
All demons have the following properties:
a) Hit dice and Gate Ability appropriate to their level.
b) Vunerability to normal weapons at Level III or less, but magical weapons only at higher levels.
c) Magic Resistance of 50% at Level I, which increases by 5% for each additional level of the demon.
d) Special abilities as determined on the tables below. Note that no demon may have both fire and ice powers.
EXAMPLE: Putting it all together, I shall now create Nasthrapur, a 6th level demon. Assume the following rolls: LI 2,6,6; LII 1,1,10; LIII 10,12,12; LIV 10,12; LV 4,10; LVI 5. Since a roll for MU level came up “3”, the demon has the MU capabilities of a 12th Level MU/Cleric.
LEVEL I: Darkness 5’ radius.
Magic Missiles (from 2-6 per day possible. Assume 4.)
LEVEL II: Fear, twice the normal range (of wand). -2 on saving throws. Read magic.
LEVEL III: Hypnotise as Illusionist.
Regenerate (2-6 pts per melee round. Assume 5 points)
LEVEL IV: Firestorm, l/day. (Since whether the demon has fire or ice powers has not been determined, this was decided randomly.) Magic Resistance raised to 80%.
LEVEL V: Fireball of 12 dice. Magic Resistance raised to 90%.
LEVEL VI: Mass Charm. In addition, he receives the normal benefits of being a 6th Level
demon: eight 10-sided hit dice, a 70% chance of gating in a Level 3 or 4 demon, and can be hit by magic weapons only.
Assume his appearance is a cross between a Red Dragon and Wild Cattle. Such a creature might have a bull’s head and hooves, but a scaly body and leathery wings. A dragon’s taloned forelegs take the place of arms. This combination will give the demon the following special abilities: bite/butt/claw attacks, flight, and a breath weapon of fire usable
three times per day that does 24 points of damage (assuming the dragon maturity roll was a 2).
Originally appeared in Dragon Magazine #13 (1978).