"Some players will find more enjoyment in spoiling a game than in playing it, and this ruins the fun for the rest of the participants, so it must be prevented. ... Strong steps short of expulsion can be an extra random monster die, obviously rolled, the attack of an ethereal mummy (which always strikes by surprise, naturally), points of damage from "blue bolts from the heavens" striking the offender's head, or the permanent loss of a point of charisma (appropriately) from the character belonging to the offender."
Players: Okay, once we wake up from our long rest, we take a short rest so that the Warlock can sacrifice Skeeter from his Bag o' Rats.
DM: An ethereal mummy materialized and attacks you!!!!!
Players: ..... gramps, have you been channeling Gygax again? We aren't playing Tomb of Horrors anymore ....
DM: YOU ARE SMITED BY A BLUE BOLT FROM THE HEAVENS!
Players: .... c'mon, now. It's going to be okay. No more save or dies.
DM: WHIPPERSNAPPERS CAN'T EVEN ORDER YOUR ABILITIES RIGHT! It's Strength, Intelligence, Wisdom, Dexterity, Constitution, Charisma. That's right, you LOSE A POINT OF CHARISMA, for KILLING SKEETER!
Players: *sigh*