Familiars and the Light cantrip

[Segev]

Maybe I am slow to only realize this little trick now, but at no point does the Find Familiar spell state that you have to see the location within 30 feet that you summon your familiar to when calling it back from its pocket dimension. Thus can let you place it on the other side of doors or even in sealed boxes, like treasure chests or sarcophagi.

Unfortunately, they cannot carry stuff, and even if they have darkvision, the disadvantage to perception for working in the dim lighting that total darkness becomes for those with darkvision is painful for the low-perception familiar. You can use a bat or crab for the blindsight, but that has its own potential limitations to what the nature of its perception might be. And in either case, your familiar will lack color vision if it is in the dark.

However, the Light cantrip is a touch-range spell. If you know it, you can cast it and have your familiar do the touching to deliver it! This means that, if you put your familiar in a dark box or room to check its contents, you can still have it light the area up to see clearly.

Obviously, this isn't something you do it you're worried something in the area will spot your familiar, but for exploring tight spaces or just checking if a box is worth opening before risking traps, a tiny spider with the Light spell could be ideal.

[Burley]

I don't know that this is a true counter to your idea, but there is this bit (https://www.dndbeyond.com/sources/basic-rules/spellcasting#AClearPathtotheTarget):


A Clear Path to the Target
To target something, you must have a clear path to it, so it can't be behind total cover. If you place an area of effect at a point that you can't see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction.

You're not targeting anything, but you are summoning something to a point within ten feet. Per the quoted rule, your familiar would appear on the near side of the obstruction, meaning the outside of the chest, door or wall.

This is definitely a "if your DM lets you do it" kind of thing. It wouldn't fly at my table.

Edit: Also, since you can choose the form your familiar takes when you cast Find Familiar, you could just have it be an Owl or Bat or Rat or almost any of them on the list, actually, because most of them have darkvision.

[Segev]

I don't know that this is a true counter to your idea, but there is this bit (https://www.dndbeyond.com/sources/basic-rules/spellcasting#AClearPathtotheTarget):



You're not targeting anything, but you are summoning something to a point within ten feet. Per the quoted rule, your familiar would appear on the near side of the obstruction, meaning the outside of the chest, door or wall.

This is definitely a "if your DM lets you do it" kind of thing. It wouldn't fly at my table.

Edit: Also, since you can choose the form your familiar takes when you cast Find Familiar, you could just have it be an Owl or Bat or Rat or almost any of them on the list, actually, because most of them have darkvision.

Certainly, some DM discretion is needed, because the rules are not 100% clear here, and can be read as you say (or read to allow it).

And I did address making the familiar be something with darkvision or blindsight: both have disadvantages compared to being able to see in a well-lit area. But they are viable.

[Greywander]

This trick also works to Misty Step through walls.

Summon your familiar to the other side of the wall.
Use an action to perceive through their senses (Misty Step requires sight).
Use a bonus action to Misty Step to a location you can see through your familiar.

I'm sure there are a lot of other tricks and shenanigans you can get up to by summoning your familiar to the other side of barriers.

It should be noted that A Clear Path to the Target is a spellcasting rule, and summoning your familiar from a pocket dimension is not casting a spell. Find Familiar is instantaneous, so the spell is no longer in effect. Also, some spells bypass the need for a Clear Path/Line of Effect, notably many teleportation and divination spells. I don't think most spells specify whether they require Line of Effect (only Line of Sight), and some spells wouldn't function properly if they did. The only spells that definitely require Line of Effect are attack spells and DEX save spells, since those are explicitly impeded by cover (and for DEX saves, cover might not affect where you can place an AoE, only how it spreads once placed). You can also have a situation where you can see a target through a transparent barrier, such as glass, which further muddles the issue since you do have Line of Sight but not Line of Effect.

It's true that it says if you try to place an AoE someplace you can't see and there's an obstruction in the way, that it will put the AoE on the near side of the obstruction. So clearly there are some non-attack spells that this will apply to. What isn't clear is if it applies to all spells, or only certain ones. And again, there are definitely spells that aren't limited by Line of Effect, so we have to assume that it doesn't apply to all spells. TBH, I wish they had been specific on this in the same way they were for spells requiring sight. That, and how NPCs react to spell components, particularly for social spells like Charm Person, Command, or Suggestion. Like, the target of your Suggestion knows you just cast a spell, even if the spell succeeds they're going to be suspicious, and they'll definitely put 2 and 2 together after the fact. But that's a different issue.

Edit: You know, it would make a lot of sense if each spell required either Line of Sight or Line of Effect. A spell that uses Line of Effect could just be shot blindly, like a Fire Bolt. Maybe you hit something, maybe nothing is over there, you don't know but you can still shoot and find out. If a spell requires sight then you can't just shoot it, which suggests maybe the spell doesn't follow Line of Effect but the effect is created at the point or creature you target. Then again, most teleportation and divination spell still don't work here, as you're often targeting something you don't have either Line of Sight or Line of Effect to.

[Segev]

It should be noted that A Clear Path to the Target is a spellcasting rule, and summoning your familiar from a pocket dimension is not casting a spell. Find Familiar is instantaneous, so the spell is no longer in effect.

Thanks, in particular, for pointing this out. I knew I had worked out that this trick was RAW-legal, but I had forgotten the way I did so.

[Aquillion]

I don't know that this is a true counter to your idea, but there is this bit (https://www.dndbeyond.com/sources/basic-rules/spellcasting#AClearPathtotheTarget)
That only applies to casting a spell. The bit Segev is using is further down in the spell (hence why you said ten feet, the spell's range, while they said thirty, the range of the ability the spell grants you below):


As an action, you can temporarily dismiss your familiar. It disappears into a pocket dimension where it awaits your summons. Alternatively, you can dismiss it forever. As an action while it is temporarily dismissed, you can cause it to reappear in any unoccupied space within 30 feet of you.

Since the reappear ability isn't casting a spell it doesn't use the spellcasting rules and doesn't require line-of-effect.

So I think it's possible per RAW. As for whether DMs should allow it, though, that's another question. On one hand familiars are already hugely powerful and useful, and steathily teleporting effects to any point within 30 feet could be too powerful for a first-level effect that consumes no resources to use (aside from the spell you're using them to deliver.) Using it with light isn't too much, but you can deliver any spell with this.

OTOH the fact is that most of what this trick does can already be done with a small stealthy familiar - it's pretty rare to have absolutely no way to fit your familiar into a spot. It also avoids the "decker syndrome" of playing out the familiar reaching someplace in general - you can just say "alright I send it to that spot" and if it's in 30 feet it succeeds. That could be good or bad depending, though.

[Chronos]

OTOH the fact is that most of what this trick does can already be done with a small stealthy familiar - it's pretty rare to have absolutely no way to fit your familiar into a spot.
And your familiar doesn't necessarily even need to be able to fit. Suppose that your familiar is currently a cat, and you don't want to spend the time and components to change it to something else: You can still unambiguously "fit" it through a keyhole, by looking through the keyhole to manifest it on the other side (even if manifesting it does require sight).

[sithlordnergal]

Yeah, this is one of the major uses for Familiars when it comes to scouting. I actually learned of this trick when a Pact of the Chain used their Imp Familiar to turn invisibile, communicate to them what was on the other side of doors, and even used the imp to communicate with others via relaying what was being said and responding.

[Willowhelm]

I’ve used the misty step trick a few times and my players have used the blind summoning option to check inside sealed vaults etc a few times too.

My favourite use was the first time though. I convinced another player to try and see what was on the other side of the door. Their familiar was summoned and pretty much instantly died. (Eventually we figured out the entire room was a giant gelatinous cube.)

Oops.

[Burley]

Thanks, in particular, for pointing this out. I knew I had worked out that this trick was RAW-legal, but I had forgotten the way I did so.

Okay, okay. So, if I accept all this (and I'm not so sure I do, you scamp), then what else could be done by the familiar? Could the familiar be summoned inside a room, scrawl an Instant Summons sigil on something for future thievery? Could it cast Glyph of Warding on the inside of a door, for future explosions? Could your familiar sneak into the king's bed chamber, cast Sequester and/or Simulacrum for a kidnapping/replacement plot?

[Segev]

Okay, okay. So, if I accept all this (and I'm not so sure I do, you scamp), then what else could be done by the familiar? Could the familiar be summoned inside a room, scrawl an Instant Summons sigil on something for future thievery? Could it cast Glyph of Warding on the inside of a door, for future explosions? Could your familiar sneak into the king's bed chamber, cast Sequester and/or Simulacrum for a kidnapping/replacement plot?

I don't have time right now to check, but if those are touch spells, the familiar can definitely deliver them.

[sithlordnergal]

Okay, okay. So, if I accept all this (and I'm not so sure I do, you scamp), then what else could be done by the familiar? Could the familiar be summoned inside a room, scrawl an Instant Summons sigil on something for future thievery? Could it cast Glyph of Warding on the inside of a door, for future explosions? Could your familiar sneak into the king's bed chamber, cast Sequester and/or Simulacrum for a kidnapping/replacement plot?

Yup, as long a the spell is Touch range, and no-one interrupts the Familiar, then yes. It can easily cast those spells.