Wizards Die Messily

Wizards aren't stable. I think this post speaks for itself pretty well; magical catastrophes are a staple of the arcane arts and there's so many different ways for things to go wrong that are more interesting than "rocks fall, everyone dies". Not all the explosion effects kill - but all of them will do something nasty.

Reasons a Wizard (or Warlock, or Sorcerer, or Witch, etc) Might Explode
1. Angered the gods
2. Ascended to the astral plane
3. Ate something funny
4. Bred two spells together that hate each other
5. Captured a spell that overwhelmed their brain
6. Cast a Wish spell and fucked up
7. Died with too many spells in their brain
8. Failed a save (pick a save, any save)
9. Lost a wizard duel
10. Orgasmed
11. Patron wants to punish them
12. Purposely triggered it just to see what happens
13. Read the spellbook backwards
14. Research gone horribly wrong
15. Ritual components were wrong
16. Rolled quadruples on casting a spell
17. Someone walked up behind them and shouted "Boo!"
18. Spell mutated too many times
19. Tried to channel too much power
20. Tried to finagle the laws of magic

d66 Ways a Wizard Explodes

11. Angelic Ascension. The wizard shines with inner divine light and ascends to become a terrifying angelic figure, growing more eyes and wings out of every pore. Save or fall to your knees singing hymns; everyone who witnesses the event is now part of a religion whether they like it or not. They'll be held to the same demands and standards as everyone else who follows that deity.

12. Birdsplosion. Everything that isn't animate for d10*10' around the wizard turns into a bird and flocks to attack people in the area (thanks, Hitchcock!). The swarm as a whole has like 5 HD, takes up a [radius] area, and gets to attack everyone in the radius once each turn. It can fly around at the speed of birds.
13. Bismuth. The wizard crystallizes and metastasizes. Oily rectangular rainbows of sharpened bismuth cut through the air itself, rooting themselves into the ground and everyone within d10*10'. 2d6 piercing damage (save for half) and pinned to the spot. Removing the bismuth that's pierced through you is going to be a challenge.
14. Bloodsplosion. Everyone within d10*10' is soaked in scalding blood (d6 fire damage, no save) as the wizard is violently exsanguinated. Anything bloodborne is contracted (no save). The wizard instantly drops to as near-death as the system you're using allows. Everything's soaked through in blood, destroying all papers and writing. You can't get the blood out of any items affected, no matter how hard you try.
15. Bone Rebellion. The skeleton war has come and you're ground zero. d20 of each bone-haver within d10*100's bones squirm their way out of their body and assemble into a great bone golem with 1 HD for each person exboneguinated. It wants the rest of your bones, and gains another hit die for every human-sized person it kills and exboneguinates. Can cast Debone once per round.
16. Cancer. The wizard's flesh boils and ruptures, reduplicating explosively to encompass a d10*100' sphere. Save to run. If you fail, you are engulfed in pulsing flesh that crushes inwards for d6 bludgeoning damage each round until someone can free you. The wizard takes 1 Stress every time their new horrible flesh is cut at, though they lose no hit points. They can try to control it by making Charisma tests, though if they fail it will act against their wishes.

21. Chain Detonation. Everything within d10*10' explodes in shrapnel, taking 3d6 damage. Everything destroyed this way deals 2d6 damage to everything within the same radius of it. Continue, decreasing the number of d6 each time until you run out of d6s.
22. Clonesplosion. Everyone within d10*10' is cloned d3 times. Each clone is d6. (1. evil, 2. more good than the PC, 3. different race, 4. different class, 5. different appearance, 6. roll twice).
23. Compulsive Murder. For everyone within d10*100' for d20 days, to gain the benefits of a rest you must murder someone.
24. Dataclysm. All information within d10*100' is wiped. Lose all backstory, name, XP, and return to level 1. You no longer know why you are here or what you are doing or who your allies are. All books and other methods of information storage are wiped as well.
25. Dinosaur. Summon a tyrannosaurus rex from 65 million years ago. You have saved it from certain death; it responds with the only thing it knows - hunger. It's basically a walking, feathery, dragon, so stat it up as such. It will eat, cronch, and swallow you whole. Armor is no match for a mouthful of six-inch enamel knives. The unfortunate wizard begins in its jaws.
26. Ennui. Everyone within d10*100' feels an inescapable wave of existential "why bother"? Charisma save to take additional actions past the first one - this applies to rounds, exploration turns, hexcrawling, etc. Wears off when you succeed your third Charisma save this way.

31. Escher Explosion. Each opening within a d10*1000' radius now leads to a different, random opening within the space (can be outside the radius). This includes pouches, but not orifices. If two openings have a size difference, anything passing through is rescaled accordingly.
32. Everyone Reincarnates. Make new level 1 characters. Randomly roll for everything; don't get equipment. They wake up in the bloody shreds of each previous character.
33. Everyone's a Wizard Now. The wizard collapses into a pile of robes and teeth. Everyone in the vicinity now has a chunk of the wizard's magical power and a corresponding little copy of the wizard's mind in their head. It'll chime in with bad advice, but you have 1 MD and can cast one spell the wizard used to know.
34. Flesh-Eating Bacteria. Everyone within d10*10' contracts a bad case of incredibly contagious and virulent flesh-eating bacteria on a random area of their body. Save each round or take d6 necrotic damage. It ends once the bacteria are removed or you succeed three times. Anyone you touch contracts it too (no save).
35. Fountain of Youth. The wizard transmutes into a well of antitemporal thaumatic energy, reversing the age of everything within d10*10' by d20 years. Things reduced to 0 or fewer years of age undisintegrate, never having existed. Touching the well after the initial burst of energy ages you by d20-10 years the first time (so +/- 10 years); each additional time roll an additional d20 and subtract an additional 10. The well lasts for years equal to the wizard's age at time of explosion.
36. Fusion. Everything within d10*10' must save or be fused into a horrifying monstrosity. The wizard doesn't get a save. Each round, everyone in the monstrosity gets to collectively vote either democracy or anarchy.  If democracy wins, a plurality of minds get to choose what they do, and if there is no plurality then nothing happens. If anarchy wins, everyone must come to a unanimous consensus within 1 minute or the turn is allocated randomly to one mind of the monstrosity.

41. God Says No. The effect that caused the explosion stops. The wizard stops. Everyone within d10*100' stops. A voice informs you, loudly and politely, that what you've done is not allowed. Time is rewound to before you considered doing such a thing, and that effect is no longer possible.
42. Gun. The wizard is transmuted into a random legendary gun (see Vault Hunter rules here) and becomes its onboard machine-spirit. It must kill something every day to remain intelligent.
43. Lightning! A massive lightning strike obliterates the wizard (4d6 lightning damage, no save) and scars everyone nearby (2d6 lightning damage within d10*10', save for half). Metal objects are charged with static electricity and remain so for the next 24 hours, attracting or repelling other metal objects (50% chance of each) as well as discharging when touched with bare skin (1 lightning damage).
44. Magic Dead Zone. d10*100' radius sphere becomes an anti-magic zone. Magical creatures, items, and effects persist for 10 minutes in the zone before disintegrating.
45. Mindbomb. Everyone randomly passes their character sheet to another character (including NPCs, hirelings, monsters, etc).
46. Miniature Sun. For 10 minutes, the wizard shines with the light of a sun. This magically leaves the wizard unharmed, but melts everything on their body. This also blinds permanently and deals 4d6 radiation damage to everyone within 10', blinds save ends and deals 3d6 damage within 100', and save vs. blinding (save ends) and deals 2d6 damage within 1000'.

51. Mutations! Everyone within d10*100' rolls d100s on the mutation table until they roll a positive mutation (they get all the mutations they roll).
52. Paintbomb. Roll 8 times on the Esoteric Colors table. Each cardinal direction is soaked in one of those colors for a d10*10' long cone. The wizard is coated in all 8.
53. Seeking Spores. The wizard's body sprouts with fungus that reaches for everyone within d10*100'. The spores are paralytic (save negates) and will grow rapidly once they encounter biomass. This weighs you down by 1 inventory slot, doubling every round until you're immobilized. Then you start taking damage as they crush you (d6 bludgeoning per round). The spores can be neutralized with fire, water, acid, etc - but there's lots of them, and growing fungi will release more spores.
54. Spellified. As a 4-die Spellify, applied to everyone within d10*100' of the wizard (they end up in the wizard's brain). They can interact in the wizard's mindscape (see Cavegirl's Astral Projection rules for how this might look).
55. Tear Open a Portal in Time. A d10*10' radius circle below the wizard becomes a portal in time to a random prehistoric era and everyone in the circle falls through. It lasts for 1 hour.
56. Teleport. Find the nearest thing that passes for a map in your campaign; whether it's the dungeon map, city map, region hex-map, world map... or sketch something quick. Then, throw a dart at it (drop a pencil if you don't have darts on hand). Everyone in the party teleports there.

61. There's a Crater Here Now! It's d10*1000' in radius. Good job. Everyone gets shunted to the outside and saves vs. being pulped by the air friction.
62. Transmuted into X. The wizard and everyone within d10*10' must save or become a random substance. Roll on the periodic table of elements, or a substance table of choice (see Mimics and Miscreants' spells section for mine). Dispel magic effects can return transmuted characters to their flesh-and-blood state.
63. Tunguska Event. Everything in a d10*1000' radius falls inwards. Save to remain standing. Stuff will fall on the characters; more saves as appropriate. The wizard, at the nexus of this shockwave, implodes for 6d6 bludgeoning damage (save for half).
64. Turn To Moon. Save vs. blindness as the wizard turns into a great orb of marble and ascends to the heavens. This absolutely obliterates anything in its path. You may save to jump off the new moon; if you succeed, roll a d10 to figure out how many d6s of falling damage you take. If you fail, you have about a minute of oxygen in your lungs. Make it count.
65. Uncontrollable Cackling. Everyone within d10*100' starts laughing uncontrollably. Save vs. suffocation, then unconsciousness, then 1d6 bludgeoning damage per round as your skeleton starts to shake apart with the force of your mirth. Passing a save ceases the cackling.
66. Vacuum. A d10*100' radius sphere around the wizard becomes airless for 10 minutes. Even the air in your lungs disappears. Every action in the bubble, without air, also requires a save vs. unconsciousness. You can survive 3 minutes without air in your lungs before irreversible brain damage. Good luck.