Dungeon Crawl Classics handles their magic is a very interesting and scary way. If you are a wizard, you are going to inevitably end up kinda fucked up the more you use your abilities. Mercurial Magic aspects combined with vicious corruption tables after failure make for a very haunting combination.
The only issue I have with using DCC is that the whole thing is so damn big and overwhelming in both scope and sheer amount of table searching so I've been looking elsewhere for an alternative that can satisfy my desire for weird fantasy with a brutal magic system. The conclusion that I came to is that Old School Essentials (OSE) would be a great choice as it is lightweight, deadly, and easy to learn so why not just bolt on the corruption table to that? And that is exactly what I did. Many of the below entries are from DCC's core book with minor changes or omissions to make it fit OSE better but it can easily be used for any OSR system out there.
Before I drop the table, a few clarifications. The list is 26 entries long. I've made Minor, Major, and Greater Corruptions into a range of results as opposed to individual tables and laid all of the entries into one, easy to reference table. The breakdown is simple, spells of level 1-3 would be considered Minor, 4-6+ would be considered Major/Greater (Referred to as Major from this point on) for easy of porting.
The process is quick and simple. If your Magic User critically fails their roll, depending on the level of their spell, you have them roll either a d10 or a d20. Spells of level 1-3 are open to Minor Corruptions and are a d10 is rolled on the table. Spells level 4+ are open to Major Corruption and therefore are rolled with a d20. The level of the spell is then ADDED to the result of the roll and the table is referenced. This helps gate lower level spells from getting really bad results and also allows higher level casters the chance to get lucky and get a possibly less shitty outcome for their hubris.
Example: Mork the Wizard attempts to cast Magic Missile and rolls a 1. Since Magic Missile is a level 1 spell, Mork will roll a d10 and add the spell level. He rolls a 6, so his entry would be 7 after adding the spell level (+1). The result is that one of his legs has now grown 1d6" and he walks with a strange gait from now on. Simple!
Corruption Table:
When a spell casting roll critically fails, roll on the table below.
Minor Corruption (1d10+Spell Level): Level 1-3 Spells
Major Corruption (1d20+Spell Level): Level 4-6+ Spells
2. Character passes out. He is unconscious for 1d6 hours or until awakened by vigorous means.
3. 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.
4. 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.
5. Ears mutate. Roll 1d6-1: (1) ears become pointed; (2) ears fall off (character still hears normally); (3) ears enlarge and look like an elephant’s; (4) ears elongate and look like a donkey’s (character also gains braying laugh); (5) ears shrivel and fold back.
6. Eyes affected. Roll 1d4: (1) eyes glow with unearthly color; (2) eyes gain light sensitivity (-1 to all rolls in daylight); (3) character gains infravision (sees heat signatures at range of 60’’); (4) eyes become large and unblinking, like a fish.
7. One of the character’s legs grows 1d6”. Character now walks with an odd gait.
8. Character’s teeth all fall out over the course of 1d4 days.
9. Character develops horrid pustules on his face and body. These pustules do not heal and impose a -1 penalty to Charisma.
10. Character’s tongue forks and his nostrils narrow to slits. The character is able to smell with his tongue like a snake.
11. 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.
12. 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.
13. Demonic taint. Roll 1d4-1: (1) character’s fingers elongate into claws, and he gains an attack for 1d6 damage; (2) character’s feet transform into cloven hoofs; (3) character’s legs become goat-like.
14. 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.
15. 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.
16. 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.
17. Febrile. Character slowly weakens over 1d4 months, suffering a -1 penalty to STR for each month.
18. 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.
19. Bodily transformation. Roll 1d6: (1) character grows scales across his entire body; (2) character grows gills; (3) character’s teeth fall out and are replaced by horrifyingly sharp ones (1d4 biting attack); (4) character develops webbed toes and feet.
20. Character grows a tail over 1d8 days. Roll 1d6: (1) scorpion tail that can attack for 1d4 damage plus poison (Save versus Poison or target loses 1d4 STR permanently); (2) scaly snake tail; (3) forked demon tail (grants +1 for DEX checks); (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.
21. 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.
22. Third eye. Roll 1d4 for location: (1) middle of forehead; (2) palm of hand; (3) chest; (4) back of head.
23. 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”.
24. 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.
25. Character’s head becomes bestial in a painful overnight transformation. Roll 1d6: (1) snake; (2) goat; (3) bull; (4) rat; (5) insect; (6) fish.
26. Decay. Character’s flesh falls off in zombie-like chunks. Character loses 1d4 hp per day. Only magical healing can stave off the decay.
27. A sliver of soul energy is claimed by a demon lord. Character experiences unearthly pain, suffering 3d6 damage, and a permanent -2 penalty to all ability scores.
