5E Rules for Invisibility and Perception

[theskyvalker]

The rules aren't as clearly worded as they ideally should have been and a lot of DMs run it based on some house rule or another. Recently, I listened to a podcast where Jeremy Crawford really delves deep into these rules and that gave me a clearer understanding of what the RAI (Rules as Intended) is in these scenarios. So, I just want to share this with the large 5E DM community on TTW so that they know what how they were intended to work and then they can take a call as to whether or not they want to run it by RAI:

Invisibility:

1. You still know where an invisible creature is unless the creature takes an action to hide. This means that you can still track your enemy's location based on other senses even if you can't see them unless they take the time to hide the other signs as well.

2. A visible creature needs something to hide behind, an invisible creature can hide at any time. You'd have to make a perception check contested by the invisible creature's stealth (passive works automatically if they roll lower, otherwise you can spend an action to roll a perception check) to find out exactly where they are (which square).

3. All attack rolls vs invisible creatures are made at a disadvantage (unless you have truesight/blindsight), even if you know exactly where they are. Their attacks have advantage against targets they can see as well.

4. Spells that specify "a target you can see" do not work against invisible creatures, even if you know exactly where they are.

5. You only get opportunity attacks against "an enemy that you can see", so you don't get AoOs against invisible enemies.

So what can you do, for example? A few options are:

- Make an AoE attack at the square you know he is on.

- Make ranged/melee attacks at disadvantage.

- Use Faerie Fire to negate invisibility completely.

What can you not do?

- Use any spell that specifies "an enemy that you can see", for example -> magic missile.

What happens if an invisible creature does take the "hide" action?

- Any creature that has a passive perception lower than the creature's stealth roll has no idea where the creature is. They must guess a square to attack or an area to use their AoE spells. On an incorrect guess, nothing happens.

- The other option they have is to roll a perception check (standard action in combat) to try and beat their stealth roll and again know their exact location. Attacks will still have disadvantage, however, and they still cannot target the creature with spells that require line of sight or make AoOs against them. They will know where they are from that moment onward until the next time the invisible creature takes the "hide" action again and beats their passive perception. A new roll will have to be made per "hide" action that the invisible creature takes that beats their passive perception.

- Invisibility does not work against Blindsight and Tremorsense, given the other conditions are in place (contact with ground for tremorsense, radius for blindsight).

Perception checks:

Passive perception is always active (might get a -5 to the score if you think that the situation warrants a disadvantage) and is a lower bound for your perception checks. Rolling an active perception check below the passive perception score means that the passive perception score is taken into consideration instead.

In Jeremy Crawford's words (paraphrased since I am reproducing it from memory) "You roll a perception check to notice something only when your passive wasn't enough to do so, since if your passive was enough you should have noticed that already and didn't need to roll a perception anyway. In this sense, passive perception is a lower bound on your awareness of the environment around you"

So if you have a trap that requires a DC 15 perception check to be noticed and a player has a 16 on passive perception, they should notice it automatically without them needing to say "I check for traps" and then rolling a check. If the player does that and rolls a 14, then many DMs will mistakenly say "you don't notice any traps", whereas the character should not have needed to roll a check in the first place for this DC.

The link to the podcast is here in case anyone wants to listen to Jeremy explain these things: http://dnd.wizards.com/articles/feat...eck-dd-writing

Hope this helps some 5E DMs out with these relatively confusing rules.

Disclaimer: Of course the DM makes the final call based on a number of factors, this post is just meant to clarify RAI. At the end of the day, whatever the DM says happens, happens. Players might want to direct their DM to this post to clarify that this is the RAI in case the DM is not aware of this but it is the DM's choice whether they want to follow RAI or not. Keep in mind that it is not DM vs the players.

[Asher]

This is great. Thanks for posting this. Do you know if they have more explaination of Unseen Attackers and Targets on page 194-195 PHB. I had this come up when a drow cast the darkness spell. If you cant see the target you get disadvantage but when they cant see you, you have advantage which cancels out and doesnt make sense.

[sarynkitamo]

Looks like it's come up before on Reddit. Seems like it does indeed cancel things out.

https://www.reddit.com/r/dndnext/com..._darkness_and/

[theskyvalker]

It does cancel out because if neither party can see each other then they are both fighting blind essentially and neither side has an advantage over the other.

[Asher]

Even if the drow is supposed to be "trained" in fighting with the innate darkness spell?

[theskyvalker]

The Drow would have darkvision but unless they can actually see they would still have the blinded condition in the magical darkness. The only way to not be blind in magical darkness is to have blindsight, tremorsense, or some ability to see in magical darkness. For example, devil's sight that is granted by the warlock fiend patron.