In the course of an answer to this question about ways to gain advantage on death saving throws, the following was proposed to gain advantage on a death saving throw:
Alternatively, you could be a Wild Magic Sorcerer, and use Tides of
Chaos.Starting at 1st level, you can manipulate the forces of chance and
chaos to gain advantage on one attack roll, ability check, or saving
throw. (PHB p. 103)
The problem to resolve:
Being at 0 hit points includes the condition unconscious. The condition unconscious includes the condition incapacitated. Being subject to those two conditions means that the Wild Magic Sorcerer has the following constraints to overcome in order to apply Wild Magic's Tides of Chaos to his death saving throw.
Unconscious (Appendix A p. 292, attack vulnerability not germane to this Q)
- An unconscious creature is incapacitated (see the
condition), can’t move or speak, and is unaware of its surroundings.- The creature drops whatever it’s holding and falls prone.
- The creature automatically fails Strength and Dexterity saving throws.
Incapacitated (Appendix A p. 291)
- An incapacitated creature can’t take actions or reactions.
Is using the Tides of Chaos an action, a reaction, or is it something else?
Raw Magic
Magic is a part of every sorcerer, suffusing body, mind and spirit with a latent power that waits to be tapped. (PHB p. 99)
Tides of Chaos is a "once per long rest" ability. Because it is Wild Magic, which is a bit unpredictable, and because it is a bit "meta-gamey" in that its function is to changes die rolls, and because a Sorcerer's magic is something inherent to the Sorcerer …
Does Tides of Chaos' characteristic as a class feature get around the problem of being unable to act for an unconscious/incapacitated character (who wants to use it to get advantage for a death saving throw) or does being the character being unconscious trump all of that?
1 Options for action being described in "Your Turn" (Basic Rules p. 69-70)
Best Answer
Yes, using Tides of Chaos is legitimate in this situation, at least until we get official errata that states otherwise (I could not find any). While you generally can't do "anything" whilst at zero hit points, you're still clinging on to (what may be your last moments of) life; you can still use your wild magic to tip the scales in your favor.
Tides of Chaos is not an ability, spell, action, or reaction, but instead is a class feature, like a rogue's Sneak Attack, for example (i.e. it modifies a specific circumstance in the class' favor). Since the RAW states it can be used for saves, this surely must include a Death Saving Throw, because it is classified as a type of save.
Granted, you can realistically only use it one time until you gain at least one hit point, since a recharge is only allowed after casting spells or a long rest, but I think it'd be exciting to use it right when you have two failures and two successes, barely pulling your character back from the brink of death...