Drinking an identified potion of hallucination or eating a corpse or tin of a hallucinogenic monster as a Knight carries an alignment penalty.

The blessed potion of hallucination, in addition to making you hallucinate, grants enlightenment (maybe a “corrupted” enlightenment where there’s only a 50% chance of seeing things you can’t see through the ^X command)

Darts can be dipped in several different potions besides sickness to get different effects. Blindness, hallucination, sleeping, confusion, etc. Implementation-wise, this can be done by overloading the corpsenm flag on ammunition to indicate which potion it’s been dipped in.