Spell Failure Tables

An idea for Spell Failure tables, borrowed and modified from Adventures into Darkness https://adventuresintodarkness.blogspot.com/2014/10/critical-spell-failures-and-wild-magic.html


When a spell fails it will likely have an adverse effect on the caster, and possibly on those around them…

These effects will also utilize the Sanity Rules

Spell Failure Probability (DRAFT)


When casting a spell, there is always a chance of failure.

Roll a d30

A Natural 1 always equals failure.


Modifiers to d30 roll:

  • Casting above level: -2 per Spell Level (Ex. A third-level MU is able to cast 1st or 2nd level spells. If they cast a 4th level spell, the roll will be at -4)
  • Converting the Spell into a Ritual that takes one hour per spell level: +2
  • Casting spell through a Casting Focus (wand, rod, staff, orb, etc): +1
  • Casting while under the influence of raw Mother’s Milk: +3
  • Casting under the influence of Transformed Mother’s Milk: +1


d30 Result Spell level being cast Effect
1 L1-2 -1 Sanity
1-2 L3-4 Roll on Corruption Table
1-3 L5-7 Roll on Corruption Table
1-4 L8-9 Roll on Corruption Table

Corruption Table


Roll a d20, subtract the Spell Level


Benign Corruption


1 – or less – Roll on Minor Corruption chart

2 – Spell fails and is forgotten for remainder of session

3 – Caster and target exchange physical locations

4 – Random monster is summoned (DM decides)

5 – Spell effect rebounds on caster (target is unaffected)

6 – Spell cannot be canceled at will by caster (or roll again if not applicable)

7 – Spell effect has 60′ radius centered on caster (all within radius experience the effect, including caster)

8 – Reverse spell effect strikes target (DM decides)

9 – All doors, including secret doors, portcullises, etc. (including those locked, Held or barred) within 60′ of caster swing open

10 or more – Caster takes 5 HP damage


On a roll of 2+ the Caster loses 2 Sanity points


Minor Corruption


1 or less – Roll on Major Corruption chart

2 – Character develops horrid pustules on his face. These pustules do not heal and impose a -1 penalty to social charisma ability checks.

2 –  Character’s skin on one random portion of his body appears to melt. Like wax, it flows and reforms into odd puddles and shapes. This is an ongoing, constant motion that itches constantly and repulses others. Determine location randomly (1d6): (1) face; (2) arms; (3) legs; (4) torso; (5) hands; (6) feet.

3 – One of the character’s legs grows 1d3”. Character now walks with an odd gait. This also causes constant, chronic back pain.

4 – Eyes affected. Roll 1d4: (1) eyes glow with unearthly color; (2) eyes lose pigment, turn pink, gain light sensitivity (-1 to all rolls in daylight); (3) character gains infravision (sees heat signatures at range of 100’); (4) eyes become large and unblinking, like a reptile (with a nictating membrane)..

5 – Character develops painful lesions on his chest and legs and open sores on his hands and feet that require d4+1 weeks to heal.

6 – Ears mutate. Roll 1d5: (1) ears become pointed; (2) ears fall off (character still hears normally); (3) ears enlarge and look like an elephant’s, as big as your hand; (4) ears elongate and look like a donkey’s (character also gains braying laugh); (5) ears shrivel and fold back.

7 – Chills. Character shakes constantly and cannot remain quiet due to chattering teeth. -15% to Spell Casting roll

8 – Character’s facial appearance is permanently disfigured according to the magic that was summoned. If fire magic was used, his eyebrows are scorched and his skin glows red; if cold magic was used, his skin is pasty white and his lips are blue. If ambiguous magic was used, his appearance grows gaunt and he permanently loses 5 pounds.

9 – Character’s hair is suffused with dark energy. Roll 1d4: (1) hair turns bone white; (2) hair turns pitch black; (3) hair falls out completely; (4) hair sticks straight up.

10+ – Character passes out. He is unconscious for 1d6 hours or until awakened by vigorous means.


On a roll of 2+ the Caster loses 3 Sanity Points

Save vs Death of suffer Paranoia.


Major Corruption

Below 1 – Roll on Greater corruption chart

1 – Febrile. Character slowly weakens over 1d4 months, suffering a -1 penalty to Strength for each month. Recovery takes place at the rate of 1 STR per week of normal rest.

2 – A duplicate of the character’s face grows on his back. It looks just like his normal face. The eyes, nose, and mouth can be operated independently.

3 – Consumption. Character’s body feeds on its own mass. Character loses 2d10 pounds in one week and suffers a -1 penalty to Constitution.

4 – Corpulence. Character gains 6d12 pounds in one month. The weight gain imposes a -1 penalty to Dexterity, and the character’s speed is reduced by 5’.

5 – Character crackles with energy of a type associated with the spells he most commonly casts. The energy could manifest as flames, lightning, cold waves, etc.

6 – Character’s height changes by 1d20-10 inches. There is no change in weight; the character’s body grows thin and tall or short and fat.

7 – Demonic taint. Roll 1d4: (1) character’s fingers elongate into claws, and he gains an attack for 1d6 damage; (2) character’s eyes turn yellow, have vertical pupils, like a cat; (3) character’s legs become goat-like, with cloven hooves; (4) small, useless wings grow from the character’s shoulderblades (bat-, bird-, or insect-like at DM’s discretion)

8 – Character’s tongue forks and their nose flattens, nostrils narrow to slits. The character is able to taste/smell with their tongue like a snake.

9 –  Small horns grow on the character’s forehead. This appears as a ridge-like, simian forehead for the first month; then buds for the second month; goat horns after the third month; and finally, bull horns after six months.

10+ Character’s skin changes to an unearthly shade. Roll 1d8: (1) albino; (2) pitch black; (3) clear; (4) shimmering quality; (5) deep blue; (6) malevolent yellow; (7) ashen and pallid; (8) texture and color of fishy scales; (9) thick bear-like fur; (10) reptilian scales.


On a roll of 2+ the PC loses 5 Sanity Points, 1 is lost permanently.

Save vs Death at -2 or suffer Paranoia.


Greater Corruption


Below 1 – The Character ceases to exist. DM fiat on how this happens. Maybe they simply wink out of existence, maybe they explode.

1 – A sliver of soul energy is claimed by a demon lord. Character experiences unearthly pain, suffering 3d6 damage, a permanent -2 penalty to all ability scores, and a permanentl -2 penalty to Sanity.

2 – Decay. Character’s flesh falls off in zombie-like chunks. Character loses 1d4 hp per day. Only magical healing can stave off the decay.

3 – Character’s head becomes bestial in a painful overnight transformation. Roll 1d6: (1) snake; (2) goat; (3) bull; (4) rat; (5) insect; (6) fish.

4 – Character’s limbs are replaced by suckered tentacles. One limb is replaced at random each month for four months. At the end of four months, it is impossible to hide the character’s inhuman nature.

5 – Small tentacles grow around the character’s mouth and ears. The tentacles are maggot-sized at first, but grow at rate of 1” per month to a mature length of 12”.

6 – Third eye. Roll 1d4 for location: (1) middle of forehead; (2) palm of hand; (3) chest; (4) back of head.

7 – Fingers on one hand fuse while the thumb enlarges. After one week, the hand has transformed into a crab claw. Character gains a natural attack for 1d6 damage and can no longer grasp normal weapons and objects.

8 – Character grows a beak in place of his mouth. Transformation starts as a puckering of the lips that slowly turns into a full-fledged bird or squid beak over the next 1d12 months. Character gains a bite attack for 1d3 damage.

9 – Bodily transformation. Roll 1d6: (1) character grows scales across his entire body; (2) character grows gills; (3) character sprouts feathers; (4) character develops webbed toes and feet.

10+ Character grows a tail over 1d6 days. Roll 1d6: (1) scorpion tail that can attack for 1d4 damage plus poison (save or target loses 1d4 Str permanently); (2) scaly snake tail; (3) forked demon tail (grants +1 Dexterity); (4) fleshy tail ending in a useable third hand; (5) fused cartilaginous links ending in spiked stump that can attack for 1d6 damage; (6) bushy horse’s tail.


On a roll of 2+ the PC loses 7 Sanity Points, 2 are lost permanently.

Save vs Death at -4 or suffer Paranoia.




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