I'm a DM setting up a oneshot. I have an idea to spice up combat a bit by giving a hydra a breath weapon. So far, the least homebrew option I've thought of is to have an enemy spellcaster cast dragon's breath on it. However, a Hydra is stated to start out with 5 heads; does this mean every head could use the breath weapon as one action?
I can only think of two possible solutions that give different answers, but both seem equally viable.
- The spell specifically says "spew magical energy from its mouth, provided it has one". Since the hydra has five mouths, it can spew from every mouth.
- The Hydra stat block says "Multiattack: The hydra makes as many bite attacks as it has heads." Since dragon's breath is not a bite attack (and according to Jeremy Crawford, not even an "attack"), it would only be able to use the breath weapon once, despite its number of heads.
The best amalgamation I can think of would be that any head can use its breath weapon, but the creature can only do it once and then can't spend its action using its multiattack. However, this sounds ridiculously under-powered, as it essentially means 4 heads miss a turn. Would allowing every head to use dragon's breath as a result of this spell be too overpowered? Are the attack actions on the hydra's stat block irrelevant in this case, because dragon's breath is not an attack?
In short: How would casting the Dragon's Breath spell on a Hydra work? Also, could each different head have a different damage type?