System shock is the generic term for the effects which cause destruction when using polymorph magic (including polymorphitis). In all three cases, the associated message is some variation on "shuddering." In real world terms this is perhaps better described as a massive trauma.
Objects have a chance of shuddering depending on type and beatitude. A wand or cursed object has a one in 3 (guaranteed for stacks of more than 4) of shuddering. An uncursed non-wand object has a one in 8 chance of shuddering. For a blessed object the chance is one in 12. The chance is doubled if the object stack is larger than 4 objects.
When an object shudders, randomly up to all but one, or one if there was only one object, is destroyed. For each object in the original stack, there is a one in (45 + Luck) chance of a golem being created. (Only one golem can be created per square affected by polymorph.) If a golem is created, then after all objects on a square have been polymorphed, up to as many objects as the appropriate golem weighs in weight units are deleted.  The game looks at each object in order from the top of the pile, and deletes it if it is of the same material as the object which shuddered to create the golem. (However, with a chance of one in (number of objects remaining to be deleted + 1), the object will only be deleted if it is not of the same material.)
Monsters have a one in 25 chance of dying without leaving a corpse when hit by a wand of polymorph, polymorph spell, or potion of polymorph. The test is done after the tests for magic resistance. Chameleons, doppelgangers, and sandestins are immune, unless the hero has protection from shape changers .
The player is not subject to instant destruction like the other classes of polymorphable things. Instead, when you polymorph randomly, a die is rolled; if the result is greater than 1 more than your constitution, you lose 1d30 hit points and abuse your constitution. This effect will not occur if you have polymorph control, or if your polymorph form is decided by polymorphing between vampires and vampire bats, worn dragon scale mail, or lycanthropy.
- "You feel shuddering vibrations"
- A polymorphed object has undergone system shock
- "The foo shudders"
- A polymorphed monster has undergone system shock
- One possible reason is that you have undergone system shock