In a fight with an Adult Gold Dragon today our delightful barbarian suffered from the effect of Weakening Breath. Our transmutation wizard used his Transmuter's Stone for Panacea to restore hit points, and cure poison, disease, and curses. Would this cure the effect of Weakened Breath?
It wouldn't help :(
Unfortunately, there is nothing in Weakening Breath (MM, 114, Basic Rules, 299) that says it is either a curse, disease, or poison. Since there is no explicit statement that it is one of things, then it is isn't. It is just a breath weapon effect with a strength save.
The dragon exhales gas in a 60-foot cone. Each creature in that area must succeed on a DC 21 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
The effects will last until either they make the save at the end of one of their turns or 1 minute passes. The mechanics for the breath are very clear. The dragon uses that action, the characters in range make a save for it. Without giving it additional qualifiers, it is simply a strength save against the attack. And then the last line provides the specific method to end it - making the save at the end of the turn.
No other mechanic to remove the effect is present because no other mechanic is listed as being able to interact with it.
The Green Dragon presents the counterexample
In the Green Dragon's attack(Basic Rules, 285), the fact that it is poison is explicit. Had they wanted the Gold Dragon to be a poison breath, they would have used the same language.
Poison Breath (Recharge 5-6). The dragon exhales poisonous gas in a 90-foot cone. Each creature in that area must make a DC 22 Constitution saving throw, taking 77 (22d6) poison damage on a failed save, or half as much damage on a successful one.
Weakening Breath is not curable by Panacea
The 5th edition version of the Weakening Breath breath weapon is not labeled as a curse, disease, or poison. As such, it can't be cured by Panacea, which says:
You remove all curses, diseases, and poisons affecting a creature that you touch with the transmuter’s stone.
In addition, spells like lesser restoration:
You touch a creature and can end either one disease or one condition afflicting it. The condition can be blinded, deafened, paralyzed, or poisoned.
...and greater restoration:
You imbue a creature you touch with positive energy to undo a debilitating effect. You can reduce the target's exhaustion level by one, or end one of the following effects on the target:
- One effect that charmed or petrified the target
- One curse, including the target's attunement to a cursed magic item
- Any reduction to one of the target's ability scores
- One effect reducing the target's hit point maximum
...which can remove most conditions between themselves, can't remove it either.
This is a marked change from past editions, where the Weakening Breath was easier to handle.
The attack of a gold dragon can be a claw/claw/bite routine or one of two breath weapons — fire in a 9” x 3” cone, or chlorine gas in a 5” x 4” x 3” cloud.
Chlorine gas is just a poison that the neutralize poison spell could handle:
A gold dragon has two breath weapons: a cone of fire 90' long, 5' wide, at the dragon's mouth, and 30' wide at the end or a cloud of potent chlorine gas 50' long, 40' wide, and 30' high.
Very little changes for the gold dragon in this edition, and the same spell helps here once more.
A gold dragon has two types of breath weapon, a cone of fire and a cone of weakening gas. Creatures within a cone of weakening gas must succeed on a Fortitude save or take 1 point of Strength damage per age category of the dragon.
We finally have the term "weakening", but in this case it is ability damage (something that doesn't exist in the same magnitude anymore). The move away from ability damage in 5e extended to the gold dragon's breath weapon. Back in 3.x, though, it was more common, and both lesser restoration and restoration spells could help with the effects.
Close blast 5; +19 vs. Reflex; 2d8 + 7 fire damage, and the target is weakened (save ends). Miss: Half damage
In 4e, this recharge power combines both breath weapons, making the fire breath include the weakened condition. You can use First Aid to allow an ally to make a saving throw against the condition, but there may also be powers (though I couldn't find one) that can end the effect immediately.
As you can see, past editions made the gold dragon's alternate breath weapon easier to counteract at least to some extent, while 5th edition's version must simply be waited out.
Weakening Breath. The Dragon exhales gas in a 60-foot cone. Each creature in that area must succeed on a DC 21 Strength saving throw or have disadvantage on Strength-based Attack rolls, Strength Checks, and Strength Saving Throws for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the Effect on itself on a success.
Nothing in this description mentions the effect being a curse, poison or disease.
So although it was a worthy try by the Wizard, it wouldn't have any chance of removing the effect.
The Panacea does not cure the effect of the Weakening Breath
The Panacea effect from the Master Transmuter ability states (Player's Handbook, page 119):
You remove all curses, diseases, and poisons affecting a creature that you touch with the transmuter’s stone. The creature also regains all its hit points.
This ability does not cure all status effect, only ones brought on by a curse, disease, or poison.
The Adult Gold Dragon's Weakening Breath ability reads (Monster Manual, page 114):
Each creature in that area must succeed on a DC 21 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws for 1 minute.
This is a status effect brought on by the breath weapon, but it is neither a curse, poison, nor disease and as such it is not cured by the Panacea.