In Dungeons & Dragons the dungeon master gets to break the rules, but only so much. The amount of breakage varies from group to group. Some DMs stick to the rules as written, only overriding them when they defy the logic of the game world. Other DMs never track hit points and just declare monsters defeated when it suits the drama of a battle.

Despite a DM’s dominion over the rules, D&D includes some rules DMs must never break—at least if they want their players to stick with the game. Oddly, these rules never appeared in print, so successful DMs learned them by observation and insight. D&D co-creator Gary Gygax made these lessons difficult for many early DMs to learn. He set an example that seemed to encourage dungeon masters to beat players. As soon as players gained an edge, Gary created something to foil them. He and his players enjoyed the battle of wits brought by this style of play. Still, Gary just aimed to challenge players and he mostly stuck to these rules that he never wrote down.

Meanwhile, struggling DMs never deduced the unwritten rules, and often unknowingly broke them to defeat the players and to “win” D&D. Eventually, these DMs either lost all their players or they learned.

What are the dungeon master’s laws of fair play?

1. Never confront characters with threats they cannot either defeat or avoid.

The avoid part of this rule is important.

In D&D’s early days, players controlled the game’s difficulty by choosing how deep to delve into the dungeon. Certainly Gary introduced tricks aimed at luring characters deeper than they intended, but he saw such traps as avoidable tests of mapping skill. The early rules made fleeing easier and clever players knew when to run. See The Story of the Impossible Luck that Leads D&D Parties to Keep Facing Threats They Can Beat.

In today’s game, DMs more often contrive threats that the party can beat. DMs can still throw deadly, even lethal challenges, but not without giving players a warning or a way to avoid the peril. See How to Scare D&D Players—Even When They Play Mighty Heroes.

2. Assume players have taken reasonable actions.

Imagine this rule worded in a more amusing way: DMs should always assume the characters are wearing pants, even if no players said that they put them on. Obviously, this guideline exempts the anthropomorphic ducks in RuneQuest.

In the more adversarial days of D&D, some DMs insisted that players announce their intent to draw a weapon before attacking. If the battle started without weapons drawn, characters wasted a turn pulling out blades. Frustrated players took to readying weapons at every sign of danger, as if just entering a monster-infested underground death trap fell short of a sign.

3. Never let players ignorantly take a substantial risk.

We all love when players stake their characters’ lives on some reckless, nearly impossible stunt. Whether they succeed or fail, such moments make unforgettable gaming. But before any foolhardy undertaking, make sure the players know (1) the odds and (2) the result of failure. I typically share difficulty classes before players roll. These DC numbers help span the gulf between a character’s vivid sense of the game world and what a player learns from a DM’s description. DCs prevent misunderstandings.

As for risks, make sure players know that, say, falling from the Earth mote means plunging into a sea of lava. That works better than rewinding the action for a player who heard “sea” and not “lava.”

4. Never plan to take the players’ freedom or stuff to support your plot.

In the early days of D&D, some gamers coached DMs to deal with excess treasure by having thieves steal it as the characters slept. Often the caper succeeded because the players never listed the reasonable precautions they would take to protect their treasures. (See rule 2.)

Early spells like Leomund’s Secret Chest seem designed to thwart thievery, so perhaps Gary indulged in such thefts. Gary had an excuse: He invented most of the game’s magic items and wanted to test them in play. His players grew accustomed to seeing gear won, lost, and melted by fireballs. Also Gary’s players probably stole from each other—they played to win back then. See Did Dave and Gary’s Gift for Finding Fun in Dungeons & Dragons Lead Them Wrong?

None of this applies to today’s game. Never take the character’s hard-won gear. They will resent the loss.

Often DMs who steal gear aim to create a powerful hook, which leads players to chase their treasure through a campaign arc. Those good intentions may make the theft seem permissible, but those schemes only make the situation worse. Such rough hooks make players feel railroaded.

The same rules for gear also apply to the loved ones players invent for their backgrounds. Those casts count as the player’s stuff. Never kill such characters to create a cheap motivation.

The most common and egregious violation of this rule comes when a DM wants players taken captive. In adventure fiction, heroes get captured regularly. So DMs dream up similar stories, and then try to force a capture despite the players’ determination to never get taken alive.

Sometimes DMs opt for capture as alternative to a total party kill. While a fair exception to this rule, don’t violate rule 1 in the process by confronting characters with a threat they cannot defeat or avoid. Save your escape-from-the-dungeon scenario for a time when players ignore warning signs, make bad choices, suffer setbacks, and ignore any chance to run. Those times happen—trust me. Then, instead of rolling new characters, have the old characters wake in chains. The players will feel grateful for a second chance.

What unwritten rules have you spotted in D&D?