Making a Magical Pool chart

[Pinjata]

So ... I'd like to ask playground to help me build a 1d12 random effect chart for a magical pool. Now this should be crazy. Any by crazy I mean WILD MAGIC crazy. Twelve effects, one of them mildly positive, one of them mildly negative. Four of them severely negative. Four of them brutally negative. One of them "I was launched onto Event Horizon" negative. And the last one - a boost demigods can dream of.

The thing about this is, boost and penalties must be benefecial to all. Casters, nanceasters, monsters. Constructs, undead and oozes.

How should I go about this? Did I miss something?

thanks

[Yahzi]

How should I go about this? Did I miss something?
You missed explaining why you would want to do this. Effectively you are creating a Deck of Many Things. In my experience the Deck is batting 100%; every campaign I have seen it used in has been destroyed by it.

Here's your list, as you described it:

1. Who cares.
2. Who cares.
3-6. Haha I messed with you good! Loser!
7-10. Roll a new character.
11. Roll a new character.
12. You win D&D. Roll a new character.

Far better is to create a pool with a theme; with some kind of internal logic that the players can interact with. Think small, because they'll abuse it to terrible ends. A DM once gave my party a pool that effectively cast invisibility; a few game sessions later he sacrificed his main villain to blow up our invisible robots of plant-death. Good times.

EDIT: To be clear: imposing significant punishments or rewards based on a single random dice roll is the antithesis of good game design. Games are about interesting choices; whether or not to sip from a pool just isn't that interesting of a choice, mechanic, or scenario. Whether or not to spare the traitor's life; whether or not to use a powerful but cursed item knowing that it aids the dark; whether or not to expose the otherwise good ruler's crime; these are interesting choices that lead to interesting outcomes. Playing Russian Roulette with a magic pool doesn't sound interesting to me.

[Pinjata]

Allrighty. I may go after Deck in the end but i guess you deserve a theral explanation what this is about.

The Pool is a relic, a power source of an old, now abandoned magic city. No (sane) casters meddle with it due to its sort-of-wild-magic properties. However, if you can respawn every time the pool affects you or just kill yourself if unhappy with results and then respawn no problemo, then this is a cool way to get more power, right? Right.
So we have this dracolich who studied things about this city for awhile, got his kobold possy to occupy the huge temple in which the pool lies and prepare everything for the master dragon to arrive. After he arrives, he also gets a mound or three of reptiloid corpses - corpses he wil posess if he is unhappy with pools' results. He plans to dip in the pool as long as he does not get 1d12+0=12 and become even more badass of a BBEG that he is.

If however PCs intend to dip their toes into OBVIOUSLY UNSTABLE AND MAGICALLY DANGEROUS POOL, well, they are free to do so. It will be at the very end of the campaign anyway.

[Elvencloud]

Actually, my current campaign DID this, and we had it to non game breaking variety. Using some Hijinks from an old 2e wild magic chart, I had her combine spells and what they ended up doing to our sorceress was... fun. In the end, the ones that mattered were that her constitution increased from a 7 to a 13, but she also contracted a disease that was slowly turning her insides into stone. She ended up having to go on an epic quest with the party to find a cure (because flesh to stone for some reason wasn't working.)

I say any negatives you do to the characters if you do that... you use as plot hooks. Any positives should not be too gamebreaking.

Alas, said character also teleported herself to a parallel universe without thinking later in the campaign... but that's a different story.

[Surpriser]

If the villain plans to switch to a new body if the results are not favorable, then obviously the alterations should be bodily in nature and not affect the mind.

My first thought on reading this was the "Wild Cards" series, where basically an alien virus randomly transforms a portion of humanity. Most of those affected die horribly (e.g. by having all their internal organs melt), others end up disabled or disfigured (including having a trunk instead of a nose or being 5 metres tall without any increase in muscle strength). But for a very small percentage, the changes end up being (mostly) favorable.

You could read up on that for references, there is even a pen-and-paper conversion, though I am not familiar with that.
Some specific effects I remember, apart from those mentioned above:

Deadly:
- Being transformed into a tree (made out of flesh, not wood).
- Overheating and being cooked from the inside
- Shattering like glass on any sort of impact
- The skin falling away from the body
- Merging with any object touched

Disabling:
- Eyes replaced by nonfunctional antennas or bug eyes
- Arms transforming into tentacle-like appendages
- Falling into a deep sleep every few days and waking up in a new form
- A voice painful to anyone else

Cosmetic change:
- Spikes instead of hair
- Changes in skin colour
- Hooves instead of feet

Positive:
- Various telekinetic abilities (levitation, projecting force fields, super strength,...)
- Mind reading and alteration
- Becoming invisible when frightened