Can I avoid surprise through my familiar?

Question

You might have seen a more complicated variant of this question going on about different types of speed but a comment by Szega made me realize that a much simpler question would probably suffice and that if ever another situation came up where I needed that more complicated answer I could simply ask a new question.

If a familiar spots a hidden enemy, but the corresponding wizard does not, how much time does a familiar need to communicate that danger to the wizard?

RulesI predict to be relevant:

While your familiar is within 100 feet of you, you can communicate with it telepathically.

A member of a group can be surprised even if the other members aren't.

Answer 1

Although telepathy the spell operates slightly differently, it's a good place to look for more info:

Until the spell ends, you and the target can instantaneously share words, images, sounds, and other sensory messages with one another through the link, and the target recognizes you as the creature it is communicating with. The spell enables a creature with an Intelligence score of at least 1 to understand the meaning of your words and take in the scope of any sensory messages you send to it.

I think the important detail is even though the communication is instantaneous, it doesn’t mean your wizard's response is. Have you ever had someone ask you a question, responded “what?”, and then within 2 seconds or so processed the question? That is basically the surprised creature's initial response in the first round.

Telepathy even if instantaneous is not appreciably faster than sound for short distances. Sound travels 100ft in 0.09 seconds. Nothing stops an unsurprised character from immediately calling out when there is danger. However, whether that can prevent others from being surprised is entirely up to the gm.

From the combat section of PHB

The DM determines who might be surprised.

Just as importantly is after a few lines.

Any character or monster that doesn't notice a threat is surprised at the start of the encounter.

Noticing a threat is different than being warned about that threat. So for me as a DM, warnings (by voice or telepathy) aren’t enough to avoid surprise unless they are made before initiative.

Answer 2

Probably not

1. There's a difference between communicating with a familiar telepathically and directly perceiving what it sees and hears. We know this, because you can directly perceive with its senses; this requires conscious action on your part and disables your own senses while you're doing it. So it's not as simple as "The familiar sees them, therefore I also see them." It would need to notice the danger and communicate a warning.

2. A creature in combat can communicate only on its turn, so to warn you the familiar would have to be ahead of both you and the enemy in initiative order:

   You can communicate however you are able, through brief utterances and gestures, as you take your turn.

   The mention of "brief utterances and gestures" makes it slightly ambiguous whether this applies to telepathy, since that form of communication is faster than speech conventionally, but I'd argue that "however you are able" does include all means of communication. There are no explicit mechanics for how communication outside your turn would work.

3. Mechanically, there's no way to get un-surprised before your first turn. If shouting a warning at someone negated surprise, then everyone would do that, and the statement that "a member of a group can be surprised even if other members aren't" would be untrue in practice.

Answer 3

You likely won't get the warning in time

Simply put, in order for there to be surprise you must be in combat.

Surprise is a part of Initiative. If you are surprised during the first round of combat, often referred to to as a surprise round in previous editions, you cannot take actions or reactions for the round.

So while the familiar would not be surprised, combat will have already started with the mage surprised. During the familiar's turn, it can use its telepathy to call out, but the mage still cannot act as they are still surprised:

If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends.

Some DMs may allow the warning to happen, but RAW, you're still surprised.

Answer 4

No.

There's no meaningful difference between telepathic communication and verbal communication in terms of what it allows your character to do. If having an ally shout "Look out!" won't save you from surprise (and it won't), then neither will a familiar's telepathy.

Telepathic communication isn't the same as the "share senses" ability you can activate as an action. If you just happened to have that ability up and running, it might potentially allow you to notice an ambush before it starts, but it's unclear whether you'd share your familiar's successful perception roll or make your own roll using the familiar's special senses (if any apply). In any case, you would be blind to your own surroundings until the start of your turn, which might put you in a bad spot for any enemies who have surprise and beat your initiative.