Solo Trap and Listen Detection

Overview

In group play, players self-declare when they search for traps or listen at doors. In solo play, the same person holds both the referee's foreknowledge and the player's ignorance, which creates contaminated decisions. This procedure resolves that tension by delegating the declaration itself to a probability roll.

The key insight: the decision to check is treated as a random event, not the check result itself. Once the decision is made by the dice, the standard game procedure resolves whether the character succeeds.

Core Procedure

Will the Character Check for Traps?

Roll a d10. The character checks if the result is equal to or below their threshold:

Threshold = 1 + Character Level + Intelligence Bonus

Level	No INT Bonus	+1 INT Bonus	+2 INT Bonus
1	2 in 10	3 in 10	4 in 10
3	4 in 10	5 in 10	6 in 10
5	6 in 10	7 in 10	8 in 10
7	8 in 10	9 in 10	10 in 10
9+	Always	Always	Always

A character of level 9 or above always checks — they are experienced enough to treat it as routine.

Will the Character Listen for Noise?

Identical procedure: same threshold formula on d10. The character listens if the roll is at or below the threshold.

After the Decision Is Made

If the character decides to check or listen, apply the standard game rules for that action (e.g., Thief listen/find-traps percentile, standard 1-in-6 or 2-in-6 detection roll, etc.). This procedure only governs whether the attempt is made — not whether it succeeds.

Design Notes

Why Not Always Check?

In group play, players forget. Dungeon crawling has cognitive load; experienced players build habits but new or distracted players miss checks. Solo play removes the natural social friction that produces forgetfulness. This procedure reintroduces realistic inconsistency.

Why Level + Intelligence?

Level models experience and habit — veterans develop automatic caution.
Intelligence models pattern recognition and attentiveness.
The combination is tuned so low-level characters are unreliable (reasonable for inexperienced adventurers) and high-level characters approach certainty (they have survived by developing good habits).

Decoupling Decision from Skill

The procedure cleanly separates two distinct questions: 1. Does the character think to try? (this roll) 2. Does the character succeed if they try? (the game's standard resolution)

This prevents a common solo pitfall: the referee-self deciding to check because they know there's a trap there.

Interaction with Published Modules

When running a published adventure solo, the referee already knows trap placements. This procedure is especially valuable in that context — it creates a mechanical firewall between referee knowledge and player agency.

Sources

https://solodungeoncrawler.blogspot.com/2022/08/checking-for-traps-and-listening-for.html