[RPG] Are there mechanical disadvantages to being unable to breathe for a handful of rounds, before you are actually suffocating

breathingdnd-5e

Several monsters (for example, the Darkmantle) have abilities that cause their victims to be unable to breathe. However, when this happens in-game my characters just shrug and say, "whatever, I can hold my breath for 4 minutes." The battle is long over before suffocation becomes an issue. Similarly for situations like running into a AOE (such as a Stinking Cloud where breathing would be ill-advised.

Are there any mechanical disadvantages to being unable to breathe, before you get to the point of suffocating?

I know the rules for Suffocating from PHB p. 183 — the question is, is there any mechanical penalty to not breathing during the minutes that you can hold your breath.

It's an interesting question as to whether, for example, the Darkmantle attack allows you to "hold your breath" or moves you directly to "choking" but that's really a separate question. What I am really asking here is, if you are holding your breath, as per the game rules on PHB p. 183, can you fight at 100% efficiency? Or should, say, disdvantage apply to attacks rolls, movement rate be reduced, etc.?

Note: Jeremy Crawford has ruled that you can hold your breath.

Q: If you can't breathe due to a monster effect (ie Darkmantle) are
you immediately suffocating? Or have Con Mod+1 mins?

A: You can hold your breath.

(See Looking for play tested house rules for combat while holding your breath for a follow-on question about whether anyone has any good house rules for this situation.)

Best Answer

Depends if you hold your breath

The player's handbook p.183 gives rules for suffocating. In brief a creature holding its breath can last for minutes but a creature that runs out of breath or is choking lasts a number of rounds equal to their constitution modifier before dropping to 0 hp.

The question then is whether a PC is holding their breath when being suffocated by, say, a darkmantle. The darkmantle monster entry says a creature engulfed is, "unable to breath", but gives us no further information. This seems to be up to the DM to rule if a given character was able to begin holding their breath, and so lasts minutes, or if the suffocation begins suddenly and they can only last a few rounds.

Personally I'd go with effects such as this happening too suddenly to hold your breath since it keeps the effects relevant in an average battle.

RAW, you can hold your breath because Jeremy Crawford says so

If we're counting JC tweets as RAW than all that matters is JC says you can. As you explained in your question this means that the suffocation part of fighting a darkmantle is unlikely to ever come up in a normal battle, and I'd say this takes away what makes the darkmantle an interesting monster. Just another strange part of 5e RAW.