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Perils are a fundamental aspect of adventure design in OSR+. While a peril can take any form—an environmental hazard, a man-made trap, a deadly fall, a magic effect—there are only so many types of harm in the system that define them. If you can master these types and know when to apply them, you can design challenges on the fly no matter the context.

Designing a Peril

The easiest way to pick out the appropriate effects for your peril is to look at the list of maleficences and compare the effect you're going for with the secondary effect of each maleficence. For example, harm that involves bludgeoning suggests the Force maleficence, whereas harm that affects the mind suggests the Psychic maleficence. Tag your peril with the name of the maleficence (you can choose more than one!).

Choose a Type of Peril

Next, you have to decide the type of your peril, either minor or major. As noted in the core rules, the fundamental difference is whether the effects of the peril are permanent and require the PCs to do something to mitigate the effects, or whether the peril goes away on its own.

There are also fatal perils, the effect of which is to put the PC on death's door, no matter how many HP or wounds they have. Falling off a tall building is a fatal peril, as is being crushed by a boulder or shot with a gun at point blank range.

Choose Status Effects

Finally, take a look at the available status effects that might be caused by your peril. More than likely, you want to adopt the ones caused by the maleficence you've tagged it with. "A burning building" might be tagged with the Fire maleficence and thus cause the Burning status effect if the PC fails to overcome it, but you might also apply the Blinded or Slowed status effects when the PC engages with it, because of all the smoke.

Assign Challenge Mechanics

Choose a mechanic to handle the roll for the peril. This can be a TN on an attribute check based on a difficulty you assign, or success at a cost and poor result outcomes you've pre-determined on a success check.

Which one you choose depends upon how you want to handle the peril's failure state: if the PCs have to "trek across a deadly glacier" and they fail, do we want the PCs to get across, but suffer consequences (a success check)? Or do we want to reinforce the status quo, and force them to try a different path (a flat TN)? Both outcomes have the potential to cause attrition, but the success check keeps the narrative moving forward.

Example Perils

  • A pit trap. A slightly raised 5x5' tile in the corridor reveals the trap. [D9 or 1d6 falling + body die for a broken bone]. If this trap were not detected, a Deft check with a TN of 9 is required to avoid suffering 1d6 falling damage and breaking a bone on the body die.
  • A deadly trek across a glacier. A poor result adds 1 hold to the journey. [M as success: Slowed or lose all consumables to frost for remainder of journey]. This peril is designed specifically for use in the journey action, as a poor result makes the journey take longer, whereas success at a cost offers a choice between the Slowed status effect or attrition of their supplies for the rest of the journey.
  • A coiled viper under a vase. Rattles ominously when approached. [M11 or 1d6 venom]. This trap, once sprung, assumes the PC is bitten, and so the roll is to resist the viper's venom.

Detecting Traps

In OSR+, there is no mechanic for "detecting traps": instead, a Perception check yields clues as to the nature of the trap, and the same reasoning as outlined in Perception checks applies.

As the GM, you need to understand how your trap works, how it's triggered, and at least one way it can be disarmed. More importantly, you have to leave yourself open to other methods the players might conceive of that could disarm it. For example, if you didn't expect the PCs to pour fresh jam into the crevices of a fire trap, but there's no fictional reason why the idea wouldn't work, reward the players for their ingenuity by letting the trap be disarmed this way.

Disarming Traps

When the PCs go about disarming the trap, you select an appropriate mechanic based on what they're trying to do in the fiction. For example, in our electric hallway trap, a Reflexes check might make sense vs. the trap's TN (or perhaps they suffer 1d6 Lightning), or perhaps if a mage in the party has the Lightning maleficence, they can do a Smart check vs. the trap's TN to absorb its electrical discharge when they deliberately trigger it.

If the players come up with an especially effective way to mitigate the peril that has no meaningful chance of failure, skip the roll entirely. (The Ranger declares a roll of rubber to wrap around his companions' boots so they may cross safely.)

Corridor with Arrows Example

As another example, consider the classic corridor with shooting arrows trap. The corridor requires PCs to pass through single file, and has slots to shoot arrows on either wall of the corridor. You decide that the trap poses a Deft 11 to avoid or else it inflicts 1d6 damage and a particular poison you've designed using the poison rules. What we want to consider here is how the PCs might go about disarming it.

  • First, if PCs examine the walls specifically, that might trigger a Perception success check that reveals the walls are a different material than the floor and ceiling and have faint rectangular outlines on them in rows. If they roll with GM advantage, you might reveal that there are thin, window-shaped outlines in the walls running down either side, sunken into the stone.
  • With this information, the PCs might decide to hold up shields on either side of themselves while passing through as a precaution, or coat the walls in goo with a spell, or examine the floor for the triggering mechanism and then attempt to disarm it by prying off a tile to break the mechanism. They might even decide to just crawl on their bellies.

Each of these approaches to disarming the trap come with different potential for meaningful failure. You might decide that crawling across the floor completely avoids the arrows, or that holding up shields would be enough to stop them from causing harm, and obviate a roll entirely. On the contrary, they might fail to fully disarm the trap by disabling the triggering mechanism, or they might fail to fully coat the walls with enough goo to keep the arrows from flying, in which case you might call for a success check to see what happens.

Magical Traps

Under the category of “man-made” are magical traps. The key to designing a magical trap is to remember that the magical trap should follow its own sort of logic that should be obvious enough for the spellcaster to work out.

Creating Advance Warning

How do we hint to players that the trap they discovered is magical in nature?

First, magical traps have enchantments placed on them, meaning they emanate magical auras like magic items. However, spellcasters in OSR+ only notice auras if they're specifically focusing on a magical object. This is similar to how stereograms work: you have to actively concentrate on the image to see the 3D shape hidden within it.

To clue in spellcasters that they ought to examine the trap's aura, you might mark the face of the trap with a mundane inscription that suggests the arcane (an ominous red door marked with an arcane symbol). Alternatively, if the trap is discovered in a wizard's study (a tome conspicuously laid out on the center of the archmage's desk), then no advance warning may be necessary as the PCs should suspect magical traps to be protecting a wizard's belongings.

Disarming Magical Traps

When a spellcaster examines the aura of a magical trap, you can use a success check to yield clues about how the trap works, or the nature of the peril it contains. The more successful the check, the more information you can share.

Example Magical Trap

For example, a trap that casts the spell Basilisk Gaze might reveal (incrementally, depending on the amount of success earned by the check) that the peril is of the Alchemy school; that it transmits a maleficence; that that it requires line of sight to work; that there is a battery involved that if discharged, will discharge the spell preemptively. Additionally, the room in which the trap is discovered might be filled with disfigured statues or hunks of stone from its previous victims. And the symbol on the face of the trap might suggest a bat wings or an evil eye.

When it comes to disabling traps, the player has to take everything they've learned about the trap and propose a course of action to disable it, while you have to remain open to any approach that seems consistent with the (albeit fantastical) logic of the trap.

Types of Magic Traps

Below is a list of types of logic a magical trap might follow in terms of how it operates. You want to determine what logic your trap follows before presenting it to your players, and then base any clues as to its operation on this logic, that way they can suss out an approach to disabling it that aligns with what you chose.

HermeticThe effects of such traps are sealed by a barrier, such as a magic sigil. Disrupting the barrier so that the magic contained within can be mitigated in a controlled way is key to disarming the trap.
PsychicSuch traps inflict their perils telepathically by making contact with nearby minds, therefore protecting oneself from psychic intrusion can protect from the trap's effects.
SemanticSuch traps are designed with a failsafe (like a ritual gesture, word, or other interaction) that can turn them on or off, much like a security system.
CapacitiveThese traps contain a loop of energy that courses through a central mechanism, and which if kept in balance will continue to make the trap function. Disturbing the mechanism or transferring away the energies that charge it will disrupt the trap.
FocalThe trap relies on a focus object to function, which may be exterior or interior to its system. Such a focus is usually disguised or protected, but without it the trap can't function.
MaterialSuch a trap requires specific consumable materials to function, which are usually in the vicinity. For example, a circle of binding might require a line of sea salt and a hunk of crystal or iron. Destroying these materials or taking them away from the trap's area of influence prevents it from functioning.
VoltaicThese traps possess a battery of some sort (like a lodestone) that converts mundane energy into numenic radiation. Removing the battery renders the trap inert.
TelesticA trap with one or more telestic anchors functions partially in the Astral Veil, either by drawing energies down from astral threads into the material, or creating a doorway between the realms for the purpose of summoning. Separating the mundane portion of the trap from its astral component prevents it from functioning.
This table is inspired by Justin Alexander's Article on Disarming Magical Traps

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