While walking through the dungeon, the players come to a dip in their path. Holding the torch aloft, they can’t quite see how long the dip is, but it descends down before leveling out and continuing.
As the group presses forward into the dip, their torch immediately extinguishes itself and plunges the group into darkness.
This is when the group feels a burning in their chest. The air coming in does nothing to fill their lungs…
Using Air as a Trap
Breathing in a dungeon is as important as it is in real life. Your players need air, and when dungeon delving that should not always be guaranteed. This week’s trap highlights a novel way to use breathing in a dungeon as a mechanic in your game and get your players to think about their environment more.
The Air Trap
This trap is as simple as it gets. The path ahead of the adventures makes a dip and then rises back to normal level. In the dip, the air is nearly devoid of oxygen and has filled with CO2. Carbon Dioxide, being heavier than oxygen, will settle to low spaces when present in large quantities.
The trap functions in two ways. First, it quenches lanterns, torches, or other flames as they all require oxygen to burn. Then it will start to affect the breathing capabilities of the team right away. If they use flames to see in the dark, they will need to try to orient themselves to quickly escape or risk passing out and dying.
In real life, inhaling a mixture of CO2 with a concentration above 8% is dangerous. No open source of CO2 will ever be 100% CO2, as oxygen and other air particles dissolve into it, but we can assume our trap has lethal levels of CO2.
Carbon Dioxide itself is dangerous since it is odorless and tasteless and you don’t feel the effects of high concentrations until it’s too late. The trap here is easily overcome by holding your breath and walking through, but an unsuspecting adventurer taking a lung full may fall unconscious in seconds.
Descriptions Are Key
This trap, though simple, is abnormally dangerous. It is on par with a save or die if there is only one party member. The key here is that the first person in will fall unconscious and the trap will quench flames. That should give your players information they need to see what is going on, but this can easily be a problem if your actual players don’t understand how gas works in general. Make sure you describe the scenario and give them plenty of time to figure things out.
If a player goes unconscious, make sure to go easy on them when it comes to recovery. Recovering from CO2 poisoning in real life can take weeks and leave you with permanent neurological damage. With DnD, the effects can be relieved after a healing spell or long rest.
Damage and Suffocating
When a player is suffocating in DnD, 5e provides a very detailed description of these rules. These rules give a round limit before the player hits 0 HP, but it does not provide any damage before passing out. This kind of trap is an all or nothing one and should be used either sparingly or with the knowledge that the players are prepared for this kind of thing.
Beating the Trap
The correct way to overcome this trap is use a light spell, which is not quenched by lack of oxygen, or rely on characters with darkvision to guide others. The players then hold their breath and walk through the area. A character can hold their breath for a number of minutes equal to their Constitution modifier. It should be fairly easy for most characters to pass the trap once they understand what is going on.
The longer the dip is the more difficult the trap is to overcome. The trap becomes most difficult when the players cannot see the end or if the path curves in any way. This trap is already hard enough since it is so sudden, but players who are prepared or have seen these before may be suited for something more difficult.
Using the Trap Effectively
The main purpose of using a trap like this is get your players thinking about the dangers of dungeon delving. Most of the time the players feel like they are invincible and charge headlong into danger. It can be important to remind players from time to time that mundane things can hide real dangers.
Join us next week when we kill a character who stepped on a rusty nail.