Do you have disadvantage on Con saves against poison while sleeping?

Question

NPCs are going to poison the party while they sleep, do the players have disadvantage on their saves?

The situation

I just started a campaign with a group where I was once a player. Their lvl 5 characters are on a ship sleeping in the spare crew cabin, but they do not know that it's a pirate ship. When they went to sleep it was approximately 3pm and the Pirate Captain found out that they may want to leave before her plan to get some treasure is put through. So she wants more info on the characters and I was planning to have the characters while they are sleeping be exposed to 'Essence of Ether' which is dropped down a small hole above deck. Since they are asleep and STR and DEX checks auto fail and you can't really stop yourself from breathing mid sleep, do they have disadvantage on a CON save?

Answer 1

In general: No.

Being unconscious does not disadvantage your constitution saves.

Constitution "measures health, stamina, and vital force." Saves of this variety are general cases of intrinsic bodily fortitude against a variety of harmful effects such as poison, disease, cold, and others that being unconscious doesn't generally affect.

In specific cases: yes.

The rules instructs the DM to consider the circumstances of saves with situational bonus or penalty. This allows for consideration of the kind of harm being resisted and the state of the character resisting it. Saving throws rules guidance:

A saving throw can be modified by a situational bonus or penalty and can be affected by advantage and disadvantage, as determined by the DM.

In this specific case: yes.

The proposition that an inhaled toxin is more difficult to resist while the target is unconsciously breathing deeply seems very reasonable to posit as a basis for disadvantage. It's a well thought out plan for a specific story case, reasonable, encourages role play, and seems fun to play out. Those are hallmarks of parts of a story that lead to good game play and fit well with making a situational modification to the saving throw.