Investigation
Full rules text, use cases, and edge-case handling for this skill.
Description
Investigation represents the ability to search, deduce, and piece together clues. While Perception notices that something is there, Investigation figures out what it means. A character with high Investigation excels at finding hidden objects, reading a crime scene, and reasoning from evidence to conclusions.
Investigation vs. Perception: Perception is passive awareness — noticing a hidden door exists. Investigation is active deduction — figuring out how the door mechanism works. Both may be required in sequence: Perception to find the clue, Investigation to interpret it.
Check
The GM calls for an Investigation check when actively searching an area for something specific or reasoning from available evidence.
| Difficulty | DC |
|---|---|
| Easy | 10 |
| Medium | 15 |
| Hard | 20 |
| Very Hard | 25 |
| Nearly Impossible | 30 |
Common Uses
- Searching a room for hidden objects, compartments, or traps
- Examining a body or crime scene to determine cause of death or events
- Deciphering a coded message or unusual document
- Finding the weak point in a structure, mechanism, or magical effect
- Researching a topic in a library or archive
- Identifying the properties of a magic item when Identify is unavailable
Passive Score
Passive Investigation (10 + modifier) may be used when the GM wants to determine whether a character automatically notices something that requires active reasoning — a suspicious inconsistency in a story they just heard, or an obvious trap mechanism in plain sight.
Proficiency
Investigation is a class skill for Wizards and Artificers, and is strongly associated with Intelligence-primary characters. Rogues and Rangers frequently take it to round out their utility toolkit. It is one of the most broadly useful skills in exploration and dungeon-delving.
Special
- Inquisitive Rogue: This subclass makes extensive use of Investigation alongside Insight, gaining Insightful Fighting from good Investigation rolls to enable Sneak Attack without an ally adjacent.
- Observant (feat): +5 to Passive Investigation (and Passive Perception) — extremely valuable for characters who serve the party's detective role.
- Detect Magic (spell): Reveals magical auras; Investigation may then determine the nature and purpose of a magical effect or item found.
- Comprehend Languages (spell): Removes the language barrier from document investigation, leaving only the Investigation check to extract meaning.
- Artificer: Investigation is a class skill; Artificers use it to examine and understand constructed devices and magical mechanisms.