"The PHB calls out system shock: ANY TIME the character is affected by unnatural/magical aging (or) petrification (or) polymorph, they must make a system shock roll or die. Harsh but vital. Haste and Potions of Speed force the fighter to run this risk. So does Resurrection and Wish. Without this check to powerful magics the campaign becomes a world where everyone is always hasted and magic-users are altering the fabric of the planet without consequence. Use it unrelentingly."
Anthony also relates an amusing anecdote about a 16th level NPC cleric, being convinced to resurrect the party's 6th level magic-user, fails his system shock roll for mandatory aging, thus depriving the party of their source of easy healing.
System shock, originally called "Probability of Surviving Spells," has been around since Supplement I: Greyhawk (1976)...that is to say, since nearly the very beginning of the hobby (for a point of reference, Greyhawk is also the supplement that introduces the thief class to the D&D game). The mechanic is very little changed between OD&D and AD&D save that the percentage chance of survival has been granulated for each individual point of constitution from 3 to 18. The original table condensed the numbers as follows:
Constitution 3-6: 35%
Constitution 7-10: 55%
Constitution 11-12: 80%
Constitution 13-14: 90%
Constitution 15: 95%
Constitution 16: 98%
Constitution 17: 99%
Constitution 18: 100%
None of the "basic" editions of the game (Holmes, B/X, BECMI) make use of system shock, and I'm not sure that's to the good of a better game. One of the knocks against all versions of basic D&D is its tendency to devolve to more superheroic fantasy with the acquisition of readily utilized, high level magic. Parties that can haste themselves with impunity, polymorph their henchmen into dragons, and raise dead with nary a concern make for nigh unstoppable forces in a campaign world, untroubled...and unchallenged...by the usual dangers and detriments of the game world.
Utilizing system shock, "unrelentingly" as Huso suggests, is a great way to make such high level magics feel a bit more dangerous to the user...a double-edged sword, certainly worth the risk in many cases, but still risky. And it's such an easy rule to implement: players write down their percentage on the character sheet (based on an ability that rarely changes), and whenever the character makes use of a risky action, the DM simply requests "Check system shock, please."
No fuss, no muss. It adds to depth of play, as players have an additional tactical decision to make, without adding a significant amount of procedural time. It extends the challenge of play past mid-levels. And it models a bit of fantasy literature with spell-casters displaying reluctance at the casual use of high powered magic. For me, that's a win-win-win.
Happy Wednesday, folks.