Does Death Strike apply to unconscious creatures?

Question

A 17th level Assassin Rogue has an ability called Death Strike (PHB, pg. 97) which applies when you attack and hit a surprised creature.

An unconscious creature (PHB pg. 292, emphasis mine):

is incapacitated, can't move or speak and is unaware of its surroundings

Given that an unconscious creature is unaware of its surroundings, if an assassin were to attack the unconscious character before any combat technically begins (so no initiative rolls), is the unconscious creature surprised, such that the Death Strike effect will trigger?

For example, slipping into the target's room at night and slitting its throat in its sleep.

Answer 1

Yes

Surprise is defined on PHB 189 as

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

Since, as the question notes, an unconscious creature is

unaware of its surroundings

it couldn't possibly notice any threats and is thus surprised and susceptible to the Death Attack.

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As an added bonus, note that page 292 under Unconscious says

Attack rolls against the creature have advantage

and

Any attack that hits the creature is a critical hit if the attacker is within 5 feet of the creature

Answer 2

Only at the beginning of combat

The PHB makes clear that surprise is only a thing that happens at the beginning of encounters: (PHB 189, emphasis added)

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

A creature may fall unconscious during the course of a battle, but it doesn't disappear from the initiative order. Instead, it acts on its initiative in order to make death saving throws.

Thus, you can use death strike on an unconscious enemy who is unconscious when the encounter begins, but not on one who has fallen unconscious during the fight.

One way to rationalize the inability to make a Death Strike is that it's a calculated, careful attack that's impossible to do in the heat of battle.

Answer 3

Surprise requires a DM's judgement:

Surprising Foes. If the adventurers eneounter a hostile ereature or group, the DM determines whether the adventurers or their foes might be surprised when combat erupts. (PHB 183)

And:

The DM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. (PHB 189)

One thing to notice about these is that they both indicate the surprised party entering combat, and Jeremy Crawford indicated in tweets that surprise only happens when entering combat (looking for tweet). This matches with the order of combat on PHB 189.

1. Determine surprise.

If attacking a sleeping creature at the start of the fight, yes. But, I don't know if RAW allows this to be surprise if the target was previously in the fray and became unconscious by reaching 0 HP...

I'd wager to guess the auto-fail on the save "wouldn't be fair." That said, if they are at 0 HP, as a rogue you should be able to make them fail at least three saves pretty easily -- You attack with advantage b/c they are unconscious, that is two saves, and you get sneak attack which is arguably another lost save as another source of damage (see the question about poison counting as a death save or not) or use a second attack that turn for the last save... And with the auto-critical, you'll likely surpass their max HP to boot. So, in that case I'm not sure if it really matters.

Answer 4

RAW, Surprise is only relevant in terms of initiative. Surprise only affects the first turn in combat. A creature is surprised when it is not expecting to fight, and suddenly is attacked.

If you notice even one opponent, you cannot be surprised. Surprise is not you being unaware of the number of opponents, it is being unaware of the need to fight at all.

You cannot be surprised in the middle of a fight.

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All that being said, since an unconscious creature is unaware that they are in a fight, they would be considered surprised.

As an Assassin Rogue, you will auto-crit (assuming you hit), on top of the potential doubling of the damage through the Death Strike feature. You also have advantage on the attack roll if you are in melee with them, as they are prone.