Often times people can get annoyed at the rules assumptions that all players are all hardcore optimizers and that they will all automatically reach for the tomes, the belts and bands, the cloaks of resistance and other stuff.
Thus monsters all have LUDACRIST stats (Yeah Im SURE that big ol lumbering jerk has Dex 38).
The easy solution is an inbuilt Vow of Poverty (Minus the Poverty). But it doesn't work for those that DON'T want the cristmas tree at all and wan't every magic item too be special.
So I give you:
VOW OF NON-OPTIMIZATION
Enough with the G+!%&! DarkVision: Unless core to the monster design (Like a Owl or a Shadow Creature of Darkness) either reduce the range of the Darkvision, or turn it into low light vision or REMOVE IT ENTIRELY.
AC Penalty: A 1 CR creature receives a -2 penalty to its Armor Class (Natural, deflection or some other form of your choice that is not lost on touch AC). The penalty increases to -5 at 3rd CR, and thereafter increases by -1 for each 3 CR it has.
Crappy Strike: At 4 CR creature, gains a -1 penalty too BAB (Except don’t reduce the attack output) and -1 penalty too natural attack damage rolls. This penalty rises to -2 at 10th CR, to -3 at 14th CR, to -4 at 17th CR, and to -5 at 20th CR. Treat the damage penalty as a natural penalty.
Attraction : A 6th-CR creature receives a -1 deflection penalty to its Armor Class. This penalty increases to -2 at 12th CR, and to -3 at 18th CR.
Weakness : At 7th CR, every creature gains a -1 penalty on all saving throws. This penalty increases to -2 at 13th CR, and to -3 at 17th CR.
Ability Score Penalty : At 5th CR, the creature gains a -2 penalty to one ability score. At 9th CR, it turns too a -4 penalty to that score, and a -2 penalty to another ability score. At 13th CR, the penalty grows too an -6 penalty in one score, a -4 penalty in another score, and a -2 penalty to a third ability score. At 15th CR, it becomes a -8 penalty too one score, a -6 penalty too another, a -4 penalty too the third and a -2 penalty to a fourth ability score. At 19th CR this becomes a -10 penalty too one score -8 penalty too the second, a -6 penalty too the third, a -4 penalty too the fourth and a -2 penalty to a fifth ability score.
Natural Weakness : At 8th CR, the creature gains a -1 natural armor penalty. It increases an extra -1 at 16th CR. If the Creature had no natural armor instead stack the penalty with its armor penalty (Or some other form of armor of your choice).
Damage Reduction Reduction: The creature gains a -5 penalty to magic damage reduction (If it has any) at 10th CR. At 15th CR, this widens too alignment based damage reduction, and at 19th CR becomes a -10 penalty.
Energy Vulnerability : At 10th CR, the creature gains a -5 penalty too any form of energy resistance (If it has any). At 20th CR, this penalty increases to -15. Do not count this penalty if this creature is obviously elemental in its nature (Such as a Mephit)
Degeneration : The creature’s regeneration decreases by 5 .Unless the regeneration is CORE to the monster design like the Werewolf. Then only decrease it by 2 by every 5 the regeneration value is EG -2 at 5 Regeneration, -4 at 10 Regeneration -6 at 15 Regeneration)
True Seeing : The creature looses any form of continuous true seeing ability, as the spell unless its core to the creature design (Like the Angel of Truth or whatever).
True Re-Build: Adjust the Feats as well, and adjust skills as well
Example Balor Demon
BALOR CR 20
XP 307,200
CE Large outsider (chaotic, demon, evil, extraplanar)
Init +7; Senses darkvision 10 ft., low-light vision, Perception +27
Aura flaming body, unholy aura (DC 23)
DEFENSE
AC 20, touch 14, flat-footed 16 (+1 deflection, +3 Dex, +6 natural, –1 size, +1 Dodge)
hp 135 (20d10+8)
Fort +21, Ref +10, Will +19
DR 5/cold iron and good; Immune electricity, fire, poison; SR 31
OFFENSE
Speed 40 ft., fly 90 ft. (good)
Melee +1 vorpal unholy longsword +26/+21/+16/+11 (2d6+13), +1 vorpal flamingwhip +25/+20/ (1d4+7 plus 1d6 fire and entangle) or 2 slams +26 (1d10+7)
Space 10 ft.; Reach 10 ft. (20 ft. with whip)
Spell-Like Abilities (CL 20th)
Constant—true seeing, unholy aura (DC 23)
At will—dominate monster (DC 24), greater dispel magic, greater teleport(self plus 50 lbs. of objects only), power word stun, telekinesis (DC 20)
3/day—quickened telekinesis (DC 20)
1/day—blasphemy (DC 22), fire storm (DC 23), implosion (DC 24), summon(level 9, any 1 CR 19 or lower demon 100%)
STATISTICS
Str 35, Dex 17, Con 26, Int 20, Wis 18, Cha 25
Base Atk +15; CMB +28; CMD 45
Feats Cleave, Combat Reflexes, Dodge, Improved Initiative, Improved Two-Weapon Fighting, Iron Will, Power Attack, Quicken Spell-Like Ability (telekinesis), Two-Weapon Fighting, Weapon Focus (longsword)
Skills Bluff +27, Fly +12, Intimidate +27,Knowledge +25(history) , Knowledge (nobility) +20, Knowledge (planes) +25,Knowledge (religion) +25, Perception +27, Sense Motive +25, Use Magic Device 25; Profession (Torturer) 24, Profession (Soldier) 24, Profession (Commander) 24
Racial Modifiers +8 Perception,
Languages Abyssal, Celestial, Draconic; telepathy 100 ft.
SQ death throes, vorpal strike, whip mastery
SPECIAL ABILITIES
Death Throes (Su)
When killed, a balor explodes in a blinding flash of fire that deals 100 points of damage (half fire, half unholy damage) to anything within 100 feet (Reflex DC 28 halves). The save DC is Constitution-based.
Entangle (Ex)
If a balor strikes a Medium or smaller foe with its whip, the balor can immediately attempt a grapple check without provoking an attack of opportunity. If the balor wins the check, it draws the foe into an adjacent square. The foe gains the grappled condition, but the balor does not.
Flaming Body (Su)
A balor's body is covered in dancing flames. Anyone striking a balor with a natural weapon or unarmed strike takes 1d6 points of fire damage. A creature that grapples a balor or is grappled by one takes 6d6 points of fire damage each round the grapple persists.
Vorpal Strike (Su)
Any slashing weapon a balor wields (including its standard longsword and whip) gains the vorpal weapon quality. Weapons retain this quality for one hour after the balor releases the weapon, but after this the weapon reverts to its standard magical qualities, if any.
Whip Mastery (Ex)
A balor treats a whip as a light weapon for the purposes of two-weapon fighting, and can inflict lethal damage on a foe regardless of the foe's armor.
Seems to work like a charm. Any obvious flaws you see?