I am having some issues trying to find a balance in what seems to me to be an overpowered spell (Find Familiar) considering its low level. I will state first that I have always considered the familiar as a very attractive archetype of fantasy literature and I’d love to have it in my games. But I think the way it is handled in DnD 5e is very disruptive for the game and, from a narrative point of view, very far from the fantasy trope of what a wizard’s familiar should be in my opinion.
I think the only way to address the problem is to change the spell, but before doing so (to my wizard player’s initial regret) I want to get other DM’s opinions first.
I am going to present my arguments against the spell as is written first, and after that, I am going to exemplify the effect that a familiar could have as the rule is written on a very well known adventure, Lost Mine of Phandelver, so that I can be told if I am misinterpreting something. The goal of using a prewritten adventure is because I cannot stress enough that what I am looking for is not ways to design adventures against the rules (more on why I don’t like/need that later), but help on shedding some light on whether maybe I am overstating its potential effects.
First of all, the narrative problem. In my opinion, a familiar should be a very special creature for the wizard, a sort of magical pet they are very fond of. It should be a creature with a name, and its survival should be of paramount importance for the wizard, being its death a great loss for them.
For example, I recall that this spell in Rolemaster required acquiring the creature by normal means, spending a week casting the spell on it and that if the creature died you had a -25 penalty for two weeks! So it was hard to get it and it was very, very bad to lose it. It was powerful, but the stakes were high.
But as the spell is written in DnD, this is just some kind of disposable resource, not even worthy of a spell slot (since you can even cast it as a ritual). You can have one familiar now and a totally different one an hour later, almost at no cost. You can even make it disappear when you don't need it and it’s going to be a nuisance for a given scene (let's get rid of the damn cat in this scene, now it is useless!). Treated this way, it seems to me a familiar has the narrative weight of a magic potion: this is, none at all. That is sad.
Second, as the spell is written, it is what would be called a “disruptive technology” for the game. I know there are a thousand forums giving advice on different ways a DM can neutralize the power of a familiar (distance, area effect attacks, etc.), and I want to stress that is not the lack of ideas on how to do it what takes me here. I have plenty. Is that I have two big problems with this approach to “solving” the problem. First, I don’t think I should warp the whole world and completely redesign every adventure to accommodate for a rule that has the power to suck the fun out of almost every adventure as it is written. I think changing that rule is a far easier and logical alternative to that. Second, I think a DM shouldn't try to design encounters where the players can’t use their special powers or use them in a very diminished form. On the contrary, the DM should design situations where the players are challenged but where their powers can shine, and there is a very thin line between challenging their powers and making them useless. DMs tend to think they are very clever designers, but players are very good at detecting when a situation has been expressly designed by the DM to counteract some of their abilities, and the third time they notice you are actively working against their powers they are logically going to be pissed off. I think it is more honest to openly state that a rule/spell is not working and just change it.
Third, and in a certain way the most important reason why I don’t like it. Familiars are going to consistently hog the spotlight of other player’s characters precisely when those characters should have their “special moment”. What’s the point in investing in that stealthy rogue abilities if each time you have to approach an enemy camp, examine the enemy’s castle defenses or scout a possible ambush, the wizard is just going to send its spider before you and map every corner of the dungeon, and at absolutely no risk and no cost, before you even have the chance of trying?
At last, I am going to exemplify the effect this spell could have on an average dungeon (not one expressly designed to purposely counteract it). As this is a first level spell, let's keep in mind that this would be something a newly created character could perfectly do. Let's examine the potential effects of a familiar as is written in some of its dungeons (minor spoilers ahead).
Cragmaw hideout: our first level wizard uses his bat familiar to spot the goblins guards (no need for the rogue to even bother). From the entrance of the cave, the bat maps out the entire cave before the characters have even set one foot in it. Exciting adventure ahead.
Redbrand Hideout: our heroes approach the dungeon from the secret passage. Unless the DM rules that the spider is too big to pass under the doors (while the player suspiciously squints at him), 90% of the basement is going to be discovered without moving a finger. Yeah, you could get them attacked with the Nothic first, but since they are probably going to send the spider through the passage before them, it is going to be discovered earlier anyway. Exciting adventure ahead.
Castle Cragmaw: the wizard sends his owl to every window in the castle to examine its contents and enemies. Again, 90% of the castle is known before even getting too close to it. Sure, the wizard should move to repeat the operation from the southern and northern limits of the castle to cope with the 100’ limitation, but that's pretty easy. There is a chance that the owl is discovered in the window, but with almost no consequence: it would be very hard to attack, and the worst thing it could happen is that they have to wait an hour before repeating the operation. The rogue is again just yawning in a corner. Exciting adventure ahead.
Wave Echo Cave: since there are no doors, characters can easily be aware of every corner of the dungeon three or four rooms ahead. You could save time and lay out before them the entire dungeon floorplan and all its enemies. Exciting adventure ahead.
I know, I know, there are ways to avoid these uses of the familiar, but it would end up being too obvious that you are working hard against it, and when they notice (and they always do), that’s very annoying for the players (oh, what a coincidence, it turns out that the goblins have a trained hawk guarding the castle for no apparent reason!).
So, to wrap things up, it seems to me that the only logical alternative is to modify the rule. As I said, I love the idea of familiars in a fantasy setting, so ruling the spell out completely is something I don’t want to do. But I think I have to adjust it so that its effects are not so disrupting for the game. I haven’t made my mind about how to do it yet, honestly, but I like the idea of “hard to get, hard to lose” that the Rolemaster spell had. And I think also that the extent of the remote senses capacities should be limited somehow too.
So, how do I handle the wizard's familiar invalidating exploration, outshining the rogue, at low to no cost?
Best Answer
Find familiar is not overpowered by itself, you are giving it too much leeway.
Maps
There are 2 ways for a familiar to map an area:
The latter is risky. While perceiving through the familiar's senses, the wizard is deaf and blind to its own senses. In turn, this means they should be immobile within 100 ft. of their familiar.
Let that sink in. If it takes 30 min. for the familiar to map the interior of a cavern, house, etc., you've got a seemingly unconscious character lying down within 100 ft. during that time:
100 ft. (30m) is a very small distance. The group needs to sneak in within that distance without being spotted, and to then stay out of sight with an "unconscious" character that has to be "woken" up if anything needs avoiding.
There's nothing simple or automatic in this.
But, wait, who's drawing the map? In order to map something, someone must draw the map. Or somehow communicate to the others what they're seeing... and have those others remember when they actually go in.
Once again, there's 3 options:
Have you ever tried to draw something someone else was describing, without that someone simultaneously seeing what you were drawing so they can correct it? Try it. It's good fun. The results are very different from reality.
If you want an accurate map, you'll need the 3rd option. It's going to roughly double the exploration time.
(If your wizard player wants to rely on memory, that's fine too. They, and only they, get a quick look at the map, and then they have to draw it from memory...)
Details
Is the wizard proficient in Investigation and Perception?
A map of the rooms is nice, but is it enough?
It takes a good Perception roll or Investigation roll to notice the unusual stonework of a hidden door, or to notice the guard dozing on a chair in the corner hidden from the door by the coat hanger.
The spider has no such proficiency; it's only proficient in Stealth.
And of course, one must consider ability scores:
This means that over time the gap between a familiar's or wizard's Perception score and a rogue's Perception score will keep widening. Especially accounting for the rogue's likely Expertise. And the same is true for Stealth.
There's a scaling issue inherent in the approach.
Senses
By @Erik.
Speaking of Perception, pay attention to special senses.
Many familiars have Darkvision 30 ft., which is nice. A notable exception however is the Raven, which doesn't. Sending a Raven in a dark place is not going to work.
Dangers
By @Erik.
A Tiny Beast such as a spider faces dangers that a character would not. For example, it's at risk of being hunted by other vermin which would traditionally avoid humanoids: rats, other spiders, centipedes, ...
This may not be an issue is a well-maintained mansion, but anywhere else, it definitely is.
Time
It's a common trope that "monsters" just stay in place until someone enters the room, but that's obviously not realistic.
While you are exploring, those monsters should be moving. One of the guard went to the toilet. A goblin is fetching food for the kitchen. Another goblin is sweeping the corridors.
This is important in two ways:
And the longer it takes to do the exploration, the bigger the discrepancies will likely be.
Let your players get bitten twice or thrice, and they'll ditch the unreliable tactic by themselves.
Unnoticed
Now, a spider is likely to go unnoticed. Especially if it keeps to the darker corner.
But an owl flying from window to window? If it's dark outside, okay, but if it's light outside, they'll have disadvantage on Stealth from the shadow they're suddenly casting. And someone's bound to wonder that owl's doing... it's a rather unusual behavior for an animal. And it looks tasty.
Speaking of:
A disappearing owl will cause alarm. That's definitely unusual.
Time Pressure
And finally, where is the time pressure?
Preparation is a good thing, however in general preparation time is limited due to time pressure: the monsters are not waiting for the players to show up -- unless it's an ambush -- and are moving ahead according to their own schedule regardless. The longer the players take to prepare, the more advanced the schedule of the monsters is... and then it's not about stopping them, it's about controlling and limiting the damage.
Or, conversely, and especially if the players are spotted, the more time they take to act, the more time the monsters have to prepare themselves, or to steal the initiative.
Time pressure should not be a staple of every single encounter, but it should not be dismissed altogether either.
So, to sum up, you're just allowing the familiar to get away with too much.
The familiar scout approach does not give a perfect map without assuming any risk. Far from it. And it should be inferior to sending a rogue in.
Also, and in another direction, the rogue may regardless prefer for the familiar to scout ahead in certain situations. Or to team up with the familiar for the scouting mission. Not all rogues are daredevils, quite a few care for their lives...