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Say a Player Character (PC) with low HP is in a Cloudkill:

When a creature enters the spell's area for the first time on a turn or starts its turn there, that creature must make a Constitution saving throw. The creature takes 5d8 poison damage on a failed save, or half as much damage on a successful one.

The PC is next in initiative and starts their turn. The only effect to resolve is the Cloudkill. It fails the save and the resulting damage is sufficient to get them to 0 HP.

Since this event occurred "at the start of the turn" and this is also when Death Saving Throws happen for a downed character, does the PC need to make an immediate Death Saving Throw, or, did has the "start of the turn" passed and the first Death Saving Throw will be rolled at the start next of the round?

I am aware of this relevant question "How to resolve multiple 'start of turn' triggers" and the accepted answer: events occurring at start of turn are resolved in the order chosen by the player.

However, since in my example the events cannot be reversed (the PC cannot make a Death Saving Throw before taking the damage), I feel that the question stands on its own.

The question is also not a duplicate of When does the Death Saving Throw happen with respect to sources of automatic ongoing damage? because the latter is asking for a PC that is already down.

I am asking for the specific instance of the turn where the PC falls unconscious due to a "start of the turn" trigger.

KorvinStarmast
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Alex Millette
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    @SeriousBri It's been reopened, and it is always nice to see a question showing the kind of research effort that this one does. (big thumbs up to Alex) – KorvinStarmast Jul 23 '19 at 12:40

1 Answers1

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No, you must start your turn with 0 HP

Under the section titled Death Saving Throws the Basic Rules state:

Whenever you start your turn with 0 hit points, you must make a special saving throw, called a death saving throw.

Before you start your turn, how many hit points do you have? If it is more than 0, then you will not make a death saving throw, because you started your turn with more than 0. In this situation you started your turn with more than 0 hit points and immediately lost hit points, but you still had more than 0 when your turn started.

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KelvintheWizard
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  • This generalized nicely; suppose you had an ability that moved someone 5' at the start of their turn. They wouldn't trigger cloudkill at the start of their turn, but would trigger it from entering. – Yakk Jul 24 '19 at 12:49