How does a DM handle an NPC who wants to kill a PC in their sleep?

I got an NPC Drow who wants to kill a PC Dragonborn so he can escape. The PC is very trusting and thinks he is fooling the NPC into thinking that they are allies. How do I play it out as a DM? At first glance the NPC just approaches the sleeping PC and stabs him in the heart. Sure, I could just let that happen. He's dead. I could "punish" a player for not taking precautions. It is not very good story telling though and sounds DM vs Player to me. We are all adults in the group and don't need that. I need a deus ex machina. Any ideas?

have the pc make perception check vs npc stealth check, if e succeeds he wakes up

Whoever has the highest passive perception wakes up and notices the drow sneaking around. That'd be a cool roleplaying opportunity and still leave a chance for combat.

Don't you have to be awake to do a perception check? Is there a disadvantage for the PC or an advantage for the NPC? I have to make an near-miss believable to the players.

Edit: I agree with you Thauraeln_The_Bold. I want to see how this would play out but I also have to keep the plot moving as this PC was separated from the others. This is just one possible outcome on my action tree, I have seduction as another... 

You said the PC is very trusting. Is it the PC who is very trusting, or is it the player? If it's the player, then you should say something to the PC like... "Would PCName feel comfortable sleeping and letting their guard down around NPCName?" Generally, it's a good thing to help newer (or poor) players play their characters well. Point is have fun, after all.

If it's the PC itself who is very trusting, I think you need to talk with your player about what that means. In a rough and tumble world that kind of PC is going to be at high risk, especially without friends around.

There's ways to escape without killing the PC. You just need to wrap your head around a different mindset for the npc that doesn't result in such a punishing anticlimax. When you think about it, killing the PC in their sleep, from the drow's perspective, could still be very risky. The PC could wake up at the last second and suddenly their assassination turns into a fight and the drow might be killed. Perhaps it's better to slip away in the middle of the night where the npc can then regroup and seek the power to kill the PC once and for all. 

Remember, evil characters aren't stupid, and don't take unnecessary risks. If you let the drow escape then you can open up a lot of cool potential plot lines with them; maybe they join the BBEG and become a mini-boss with their new power. Maybe they kidnap one of the PC's loved ones and the party has to rescue them while the PC wrestles internally with their own culpability for the npc's survival. Lots of fun RP opportunities out there. 

Thanks dadacomputer and CharlesThePlant. Good ideas. Yes, both the player AND the character are naïve. I think he is playing the Dragonborn right (-1 int and cha). He thinks that he can fool the Drow into being allies so he might do stuff that could comprise himself. I am ok with that. I just want to plan for the worst case.

The NPC killing the player is just one possible action. The Drow could also run away, enslave him, or seduce him. In my mind the Drow isees an opportunity to do harm to an enemy. He already tried to run away.  He was captured in a chase and lost his mount so it will be difficult for him to escape in a bad environment (lots of skies and sun as well as a ranger). I am curious to see if the PCs take advantage of an Immovable Rod. I really want the seduction to happen as I want to see where it goes but I will leave that up to what the players do.

I think you'd be fine just handwaving it: "You suddenly wake up in your inn room around three in the morning. The drow is standing over you with a knife and a murderous look. You've got no gear within reach. What do you do?" It puts the character at a serious disadvantage, being alone without their armor or equipment, but gives them the choice of how to react. Ideally, this happens at a small wilderness inn, so the characters aren't all together and the drow can steal a horse (maybe the innkeeper's) to escape if it comes to that.

Also, I'll be honest: attempting to seduce a player character sounds like a very bad idea, for many, many reasons. So much so that if it happens, I'm very interested in hearing how it went.

I’m struggling with some of the logic here.

The PC thinks he can trick the Drow into believing they’re allies, but the PC is also very trusting of the Drow? That makes no sense to me. If the PC trusts the Drow, why would he think he needs to trick them into anything?

also: is the Drow anything? A fighter? A sorcerer? An assassin? Just some random Drow? What’s the setting? Where are the other PC’s? Is no one keeping watch?

also #2: seduction isn’t automatic. Why would the seduction work. A high roll (even a nat 20) is not an automatic success. Is the PC attracted/interested in the Drow? If so, why?

Course could always set the guy up as a future baddie assassin. Sort of intentionally knocking em out and then putting a rope, a candle, and a knife aimed down at them. While a stable, but one death save situation. If a bit of tension is needed. Maybe the guy could have a candle with metal nails to ding into a metal base. (like an alarm clock on a candle) This is so that above it, would be a dagger that would fall and kill the person while giving a chance for people to respond. Since usually when alarm is called, the question of who dons armor is a big thing. A reasonable enough time for an alarm to wake people and a chance for some consequences to happen. But big thing is after you gave a chance and ability for revenge and revival.

Also an insight check since this is sort of what an entire check is based on and the observant feat also gives a big passive bonus to. Insight is kind of key and maybe can give it a try before bed. Something along the lines of the guy sleeping with a knife and some armor to avoid exhaustion. I presume a few hints have been dropped by this point. So the big thing is a chance. if going to get the drop on them, maybe a critical strike that would really weaken them. Then combat since nobody likes a no chance fight. 

This also allows for a means to escape and such. Maybe caltrops since people usually don't wear metal boots to bed. If player dies. a chance to bring them back and hunt the guy from a dropped note with something that may help bring the dead member to life. As well as a chance to make use of spells like dream, or a hint about a possible large threat. Maybe a strange picture or ominous note about a future event. Maybe tie it in as something as to why it was important for that persons character specifically would die. 

There are rules for waking sleeping NPC's and Players in Xanathars guide page 77 I believe. In summary the rules state that. 

While a creature sleeps, it is subjected to the unconscious condition.

A creature that is naturally sleeping, as opposed to being in a magically or chemically induced sleep, wakes up if it takes any damage or if someone else uses an action to shake or slap the creature awake. A sudden loud noise — such as yelling, thunder, or a ringing bell — also awakens someone that is sleeping naturally

Whispers don’t disturb sleep, unless a sleeper’s passive Wisdom (Perception) score is 20 or higher and the whispers are within 10 feet of the sleeper. Speech at a normal volume awakens a sleeper if the environment is otherwise silent (no wind, birdsong, crickets, street sounds, or the like) and the sleeper has a passive Wisdom (Perception) score of 15 or higher.

Now, in terms of the NPC attacking the player, as soon as the player takes damage they wake up, unless your players are very low level it is unlikely that being stabbed in his sleep will kill the PC. Mechanically the NPC get advantage on the attack, the attack counts as an auto Crit if it hits. You say the NPC is using a dagger, so you are looking at 1d4 damage (double dice so 2d4 cos its crit) plus any additional damage from strength modifiers etc. If the NPC is a rogue it will get sneak attack damage as well. But otherwise it really doesnt get omre then that. As soon as the attack happens the player wakes up, at this point I would probably give the NPC a second attack round to account for the player processing what is happening, this will not be an auto crit but would be at advantage, and then, roll initiative.

So if the dagger is the weapon of choice and assuming a +4 to damage (which would be high) at worst your player will have suffered 24 points of damage if all the dice rolls go against them (rolling 4's for damage, criting on the second hit). This is unlikely to kill the player. Of course, alternatively the Drow could miss both attacks (they do not auto hit a sleeping enemy) meaning they wake the player up but do no damage. 

Switch out the dagger for a garotte. A garotte causes a creature to suffocate and will kill them after a number of turns equal to their constitution modifier. This allows the player to attempt to fight back, or try to wake up the other party members to come save him before he suffocates. 

I'm with some of the others in not understanding the scenario.

1) The OP refers to other party members but makes the situation sound like the Dragonborn and the drow are alone with the Dragonborn happily sleeping. Where is the rest of the party?

2) The drow already tried to escape once. They clearly don't want to be there so how can the party or the Dragonborn expect them to just peacefully sit there and not try to escape again? Even a naive character would be aware of the risks. It seems clear that the player understanding of the situation and the DM understanding is a bit of a mismatch. For some reason the players seem to think that they can trust this NPC.

3) Seduction is never a given and may or may not be appropriate depending on the players. However, how is this seduction supposed to happen with all the party hanging about?

4) The drow appears to want to escape. There is a ranger in the party which means that they can probably be tracked. This means that the drow will have to choose exactly when to escape. In addition, unless the Dragonborn is also the ranger then the drow should have very little interest in them since killing a random party member is not going to help their escape plan.  Kill or incapacitate the ranger, steal all the horses, ride off on one ...

5) 5e doesn't have insta kill rules - anything like that is a DM call and probably home brew. At best, 5e allows for an attack at advantage with auto-critical if within 5' vs an unconscious target.

6) What other abilities and resources does the drow have? Keep in mind that the drow will travel at night (the OP mentioned lots of sunlight but that also means darkness the rest of the day when the drow may have an advantage with their enhanced darkvision. Also the sunlight sensitivity only applies during daylight. If they escape at night and can press on during the day keeping their lead then the following night they can open up their lead and possibly avoid pursuit. It does require staying up for a day but in this case, the drow may decide it is worthwhile if it allows them to escape.

Quote from David42 >>

 

5) 5e doesn't have insta kill rules - anything like that is a DM call and probably home brew. At best, 5e allows for an attack at advantage with auto-critical if within 5' vs an unconscious target. 

And this raises and important point about HP.  

HP is not "life pool" but represents awareness, wounds, fatigue and general "battle heartiness".  A high level fighter might be able to get stabbed in his sleep but only a highly trained assassin (with really beafed up stats) can critical all the way to a full HP to 0 situation.  You could, realisitically play that out.  The dark elf stabs him in night, and the PC wakes up with a knife in the side of his chest.  It hurts like something but then he wakes and pulls it out and combat starts.

Here's how I would run the challenge... The Drow makes a stealth check. Run their stealth check against every character in the room's Passive Perception -5 (something like -10 would probably make more sense, but -5 is more just to give the players an actual chance of success). If the drow fails to stealth low enough any players to catch them wake up to the sight of their prisoner with a big knife ready to attack... roll initiative and remind the players they can't shout to wake everyone else up until it gets to their turn, so if the Drow beats them in initiative they still have the opportunity to make the assassination attempt, although if they're intelligent they might try to run or surrender. If they do manage to make their stealth check to attack the player they get a single auto-crit attack on their intended target... as long as everyone's at least level 5 and the intended target isn't a wizard or sorcerer, odds are decent they'll survive at least long enough to shout for help and then everyone's awake and we roll initiative from there.

Personally as a dm in this position my drow first of all are great at poisons and concoctions created from natural elements, all drownin my world have some knowledge of that, so the drow would try to drug the players, slipping something in a drink or food. Just a little something to knock them out and leave them sleeping. 

This then means that if the players fail a constitution saving throw they sleep through any combat, or even have the players come around to the sight of the player bleeding out, having to make death saving throws while they try and work out what has happened and save his life. In fact for a drow wanting to escape forcing the party to lose time in the chase  trying to keep the player alive vs simply waking up to him being dead allowing them all to chase after her hurting the player almost to death but not quite would be the way to go, stabbing with a poison blade so forcing the party to keep him stabilized as he loses health each turn until the poison is cured or loses potency. 

Quote from mtbrocket >>

How does a DM handle an NPC who wants to kill a PC in their sleep?

I got an NPC Drow who wants to kill a PC Dragonborn so he can escape. The PC is very trusting and thinks he is fooling the NPC into thinking that they are allies. How do I play it out as a DM? At first glance the NPC just approaches the sleeping PC and stabs him in the heart. Sure, I could just let that happen. He's dead. I could "punish" a player for not taking precautions. It is not very good story telling though and sounds DM vs Player to me. We are all adults in the group and don't need that. I need a deus ex machina. Any ideas?

 This is just confusing for a lot of reasons.

Firstly, as others have mentioned if the end goal is to escape, there are tons of ways to do that without killing any PCs. So just... choose not to kill any PCs. I feel like the problem is entirely due to something you have complete control over. No deus ex machina is required here, just a change in your approach.

Secondly, why does the PC with terrible INT and CHA think he can fool the drow? Sure he's gullible, but is the whole party blind to it? Forrest Gump was not a smart man, but he knew he was not a smart man. And certainly others did. Can no one in the party pull him aside and say, "Hey, you're not as deceitful as you think you are. You're not fooling the drow at all"?

Thirdly, who is this drow that you're not sure whether they'd kill, seduce, or enslave? You need to fill in this NPC and give them motivations at the moment they get captured if not before that. Maybe they are very scheming and prefer to manipulate their captor into doing what they want. Maybe they favor more indirect methods of harm and would prefer to escape and then constantly hinder/harass/attack the party from a position of safety by spreading rumors or hiring thugs to ambush them. What they are probably not is a brutal murderer who happily slits everyone's throats - simply because that doesn't work for your story. So just pick something else - literally anything else - and go with it.

Thanks everyone for your great responses.

We played on Sunday. I ended up not having the NPC drow attempt to kill the dragonborn PC as the players were so diehard sure their plan to befriend the drow and infuriate the enemy forces would work I just had to see where it would lead. The dragonborn helped the NPC drow escape captivity, race across the prairie, andddd....promptly fell asleep. Bring on the dream of a female dragonborn...(planting the plot seed for latter use. He he.)

Anyway a bit latter the PC goliath finally caught up and tried to stealthily throw a rock at the PC dragonborn with a note identifying exactly what tree he was behind. Needless to say it is not possible to stealthily land a rock, not a pebble, a rock...roll initiative. These guys are the Keystone Cops I swear. But we all are having fun. Now we just need more players.