Complete Guide to the Insight Skill in D&D 5e
Do you want to be a human (or whatever race you are playing) lie detector? Well that’s the job of the Insight skill, and just about it’s only job at that. It can also be used to determine a creature’s mood or the intent behind their actions or words, though those things are normally more apparent and may not even require a skill check. So, let’s get into how lying and persuading works in 5e.
When you are conversing with another creature (verbally or non-verbally), either of you are free to make Insight checks to determine the validity and intention of what the other is saying. Lying on its own does not inherently prompt an Insight check, it is up to the creature or player to determine when is correct to make that check. Now, before you go rolling Insight checks after every sentence that every NPC speaks, know that this is wildly unnecessary. If you feel that you the conversation may proceed differently if you determine that what was just said was a lie, then yes, make a check and let it help you decide how to proceed. However, simply waiting until the end of the conversation and asking your DM for an Insight check concerning it will be plenty enough for you to learn if you can trust what you just heard.
For DMs, let’s talk about how to run Insight checks, because it can be a bit tricky. Let’s say you just had an NPC lie to the party, and they are suspicious of the lie, so they ask to make a check. First, don’t let the entire table roll. Group checks like that aren’t good for the game for multiple reasons, but chief among them is that someone is bound to succeed by probability alone. Let the person with the highest Insight bonus roll, potentially with advantage of the entire group is also suspicious, as that could be interpreted as the help action. The DC should be variable. If your NPC actually did lie, make them roll a Deception check, and have the result be the DC of the Insight check made by your player. If the NPC did not lie, use Persuasion instead. Don’t announce the DC to your player. Next, have variable degrees of success. If your player passed the check, they discern if it was a lie or the truth. If they just barely failed, then they are suspicious, but not convinced either way. If they fail by 5 or more, then you can either choose for yourself, or have the player choose if they believe what was said was fact or fiction. This makes high Charisma creatures almost dangerous to make Insight checks on, and will help dissuade players from constantly rolling Insight checks.
Lastly, I want to talk about passive Insight. This isn’t written down on your character sheet like passive Perception, but it works the same way. You get your passive Insight by adding 10 to your Insight bonus, and you always can see through any liars you hear whose Deception check is less than it. The Observant feat (as terrible as it is) specifically calls this out, so this isn’t something I just came up with. Theoretically, every skill has a passive version, but they don’t really get used very often.
To summarize, players, be kind to your DM and don’t spam Insight checks constantly, and DMs, punish players for failing the check. We punish failing every other check in this game (mostly), so why should Insight get a free pass?
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