Yes, but these...

I love monster modification tables. I love rolling dice to make things more horrid. I reckon most DMs love these things.

Here are some universal monster modifications to throw your players a curve ball shaped like an exploding ogre with beholder eyestalks. Zombies are too boring? Now they are immune to fire and self-immolate as they hug and munch your PCs brains. Griffons in your campaign are now inexplicably afraid of parchment and have a predilection for devouring gold and silver.

Roll a few times on the d12 table and add the results to your next random encounter.

Yes, but these ______s:

1. Explode in a 10' area when they perish. (Roll d4)

Displacer Cubes: Because your DM hates you.

1. Fire or burning ash
2. Acid
3. Bone and viscera
4. Poison cloud

2. Are immune to fire and... (Roll d4)

1. Self-immolating
2. Breathe fire
3. Immolate others psychically
4. Break into smaller flaming selves when wounded

3. Are immune to cold and... (Roll d4)

1. Covered in thick ice armour
2. Have a cone of cold breath weapon
3. Creak and moan like ice breaking (morale breaker)
4. Are the frozen vessel or prison of another entity

4. Has dangerous blood (spatters attacker like a counter-attack). (Roll d4)

1. Acid
2. Contact poison (kills in 1d12+Con rounds)
3. Causes insanity through horrific visions
4. Causes petrification

5. Are really cyborgs or machines. (Roll d4)

1. Clockwork
2. Advanced tech (looks totally realistic with fur and flesh covering tech)
3. Steam-powered
4. Alien tech

6. Are Undead (if already undead, then they are positive energy undead). (Roll d4)

1. Level drain
2. Steal vitality (Ability drain; heads - STR, tails - CON)
3. Mindless and murderously motivated to destroy the living
4. Must consume living flesh

7. Is a shapechanger; takes the form of: (Roll d4)

1. Any animal
2. Any humanoid
3. Anything it can see
4. Anything at all

8. Consumes unusual material for sustenance/powers. (Roll d8)

1. Gold or silver
2. Non-precious metals
3. Gemstones
4. Magic
5. Eyes
6. Bones
7. Fetuses or newborns
8. Sex organs

D'aww! Chaotic Cute!

9. Has an alignment diametrically opposed to the nature of its kin: a Chaotic Evil Gold Dragon or Chaotic Good Baatezu, for example. OR Roll a random alignment below and remove results of the current alignment of the affected creature. (Roll 2d6)

1. Lawful
2. Chaotic
3. Neutral
4. Evil
5. Good
6. Unaligned

10. Has an unusual weakness. (Roll d6)

1. Water deals damage as fire
2. Aversion to paper or papyrus, flees from it
3. Fearful of children (or halflings)
4. Allergy to Gold (suffers mortal wounds from gold weapons)
5. Specific spices, seasonings or salt
6. Flowers, specific types are poisonous

11. Composed of powerful magic, can be dispelled. Power source: (Roll d8)

1. Necromancy
2. Elementalism
3. Blood Magic
4. Heliomancy or Lunomancy
5. Divinity
6. Fae Magic
7. Hateful or Righteous Force of Will
8. Madness

12. Has the combined powers or physical parts of two or more creatures. (Roll d4)

1. Eats the heart or major organs to steal strength from victims, takes one power temporarily for each organ consumed
2. Spliced together by mad scientists
3. Hellish abomination, twisted and insane
4. Polymorphed composite of two creatures, as by Polycorporation

New LL Spell: 

Polycorporation (MU 5)

Duration: Permanent*, Range: 10’ 

Two creatures are mystically combined. This bonding can be undone by another polymorph spell or a dispel magic spell. AC and HD are added together and halved (half HD are added as +1 per remaining HD). Saves are based on the higher HD creature. All abilities, defenses and attack modes are retained. *Willing creatures can remain combined indefinitely. Unwilling subjects of the spell can throw off the effects after a number of turns equal to the caster’s level+6.

New Monster:

Corpidius, a powerful sorceror, has decided to polycorporate the orcs in his service with the displacer beasts (or phase tigers) from his breeding pens. The result is a terrible bloodlusting hunter with 10 limbs.
Displacer Orc: a six-legged tauric creature with two arms and two whip-like tentacles emerging from the shoulders. 

• AC: 5 (6/4) 
• HD: 3+3 (1/6, half level becomes +3) 
• Morale: 10 
• Attack: by weapon, shoulder whips 2d4/2d4 
• Defenses: displacement, all attacks against a displacement orc are -2 to hit and saves are made at +2 
• Saves as F6