Sneak attack on 5e with surprise?

The story is that our DM had an NPC who essentially "joined our party" but was actually an enemy rogue. In the middle of combat, the NPC ran up and attacked a party member, which the DM deemed as a surprise attack and allowed him to get sneak attack. The goal was basically to one shot a low-level character while the rest of the party was unaware.

The question is: is it normal to allow a rogue to get sneak attack in a situation like this, where the attacker isn’t hidden and otherwise doesn’t have advantage?

I know in the end it’s pretty much up to the DM’s discretion, but I can’t find where that fits in the rules, and it almost resulted in a one-hit KO.

Can Alert prevent Surprise if you don’t know the enemy exists?

In a large dark temple, a player with the Alert feat and Darkvision can only see out to 60 ft, but at 100 ft there is an enemy with 120 ft Truesight sitting in a Silence spell and firing a crossbow. If the player rolls 20 for initiative and the enemy rolls 10, does the player get to attack first? Or should the enemy get to fire the shot before initiative is rolled? Or should the enemy roll initiative for itself, fire a shot, and then have the player roll into the initiative?

Can Alert prevent Surprise if you don’t know combat is occurring yet? [duplicate]

If part of the party enters combat with enemies but the rest of the party is not aware of the threat or aware there is combat happening yet, does a player with the Alert feat who rolls highest on initiative act before even the enemies?

In this example, the Archer has the Alert feat but is hanging back behind a corner waiting for the Paladin to see if things are safe. The group rolls Initiative and the Archer rolls 21, the Spiders roll 15, and the Paladin rolls 8. The Spiders roll 24 for Stealth and Surprise the Paladin.

Who acts first? The only answers I come up with seem to unfairly negate the Archer’s choice to take the Alert feat.

enter image description here

The relevant part of the Alert feat:

You can’t be surprised while you are conscious.

Can I avoid surprise through my familiar?

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.

How does the Gloom Stalker ranger’s Dread Ambusher feature interact with Surprise?

In D&D 5e, if a Gloom Stalker Ranger uses their Dread Ambusher feature’s secondary attack on a creature during a surprise round (whether on the same target or a different one), is that creature still considered surprised?

This is important if the character is multiclassed with Assassin rogue, because Assassins auto-crit when hitting a surprised creature.

When exactly does combat start and surprise take effect?

So say I’m going to ambush an orc. I successfully sneak up on him and I attack. The DM determines that the orc is surprised. The orc happens to get an initiative roll of 19, while I get a 10. How would this work? I can only think of two reasonable resolutions to this.

  1. The orc, having a higher initiative, goes first. Since he’s surprised, he does nothing. Then it’s my turn. If the orc survives my attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.
  2. I, having started the combat, go first. If the orc survives my attack, but he is surprised, so he does nothing. It is now my turn again, I attack again. If the orc survives my second attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.

Which one of these is correct? neither? Does starting combat secure me a turn/action at the start of initiative order like in option 2? If option 1 is correct, could I ready an action to shoot the orc, effectively granting me a similar first attack as in option 2?

Sorry if this makes no sense.

Can Nerveskitter be cast during a surprise round, let’s say directly when you are aware that you are being ambushed?

  • Let’s say my group is ambushed and no one is aware, the ennemies then have a surprise round against us.
  • As soon as I am aware of the attack (they could jump/charge in front of us, shoot an arrow AND hit someone (could be me), cast a spell and I could hear it with a very good listen roll etc.) can I cast Nerveskitter or is no action allowed at all?
  • Take note that in 3.5 Nerveskitter states:

    (…)Unlike other immediate actions, you can cast this spell while flat-footed(…)

So with all this info, if I was to have a contingency spell (Celerity) with the condition: Whenever I cast Nerveskitter: Activate.

What would happen? I would be able to act right away, then the rest of the surprise round would happen (let’s say I’m immune to daze or I resisted with the Quick Recovery feat) then what?:

  • Do I start first and I do not need to roll initiative?
  • I still need to roll for initiative?

RAW answers if possible (FAQ, 3.X, I would normally allow pathfinder as well but nerveskitter was nerfed in pathfinder)

Does a single PC who is stealthy get to surprise monsters when the rest of the group is not?

The rules for a surprise round, seem to be focused on the people being surprised. (They lose a turn) rather than being focused on the people doing the surprising (They get an extra turn)

The rules are clear, that each person in a group can be surprised, even if other people in the group are not surprised. So if a party is ambushed by a single stealthy carrion crawler, some members of the group will lose a turn (be surprised) and others will not (they get to act normally).

However, I’m not clear what happens if two groups approach each other, were some members are being stealthy and others are not.

For example, I have a Rogue who is being quiet and stealthy and rolls a 20 on their stealth check. The rest of the group however (Fighter and Wizard), is just marching along at a slow pace. They turn a corner, and see a group of 4 goblins, with a passive perception of 13. Do the 4 goblins lose their first turn because they are surprised by the rogue? Do the Fighter and Wizard get to act on that first turn?

Another example, Same two groups. Two of the goblins rolled a 20 on their stealth, and the other two rolled a 5. Are the Fighter and Wizard and Rogue surprised? (They lose their first turn) Or can they only attack the two goblins with a stealth of 5?

Surprise confusion

I’ve been reading information about the surprise mechanic and still confused on which to use. There are 3 methods of Surprise that I see all over the internet.

First: Group Surprise Check

To make a Group Surprise Check, half or majority of the PCs must beat the highest passive perception of the monsters to succeed the surprise.

Second: Fail one Stealth, not all is surprised.

If one of the PCs rolls (Stealth) lower than one of the passive perception of the monsters, the Surprise is botched for everyone.

Third: Some are surprised, some are not.

PC 1 rolls 14 PC 2 rolls 14 PC 3 rolls 12 PC 4 rolls 11

Monster 1 with PP of 15 Monster 2 with PP of 15 Monster 3 with PP of 13 Monster 4 with PP of 10

PC 1 and 2 surprises Monster 3 and 4, but not Monster 1 and 2

I know the Group Check can be an optional check for this. But what about the Second and Third checks? Which are true? Which should be used?