How do patrons with non-energy breath weapons interact with a Dragon Herald's (Bard Archetype) benefits?

Question

So, the Dragon Herald (Bard;Kobold) archetype has a couple abilities based on the energy type of the dragon the herald chooses as their patron. The wording of the archetype allows for any type of true dragons to be chosen as the patron.

The two abilities I'm wondering about are Coat of Arms (Ex):

A dragon herald gains energy resistance equal to her dragon herald level against the energy type associated with her dragon patron. This resistance stacks with any inherent racial resistances, but not with magical or temporary resistances.

and Rebuke Foes (Su):

At 12th level, the dragon herald gains the ability to rain down her patron's wrath on her enemies, dealing energy damage of the appropriate type equal to twice her dragon herald level (Reflex save for half). She can target one enemy within 50 feet for every 4 dragon herald levels she has. This effect occurs once per round for as long as she continues her performance.

Your standard metallic/chromatic makes sense (Acid, Fire, Cold, and Electricity are pretty straight forward), but there are some other true dragons that are less straight forward.

The (Imperial) Forest dragon has a breath weapon that does piercing damage, and the Guardian Dragon does con damage from poison. How would you handle these energy types? They're technically true-dragons (I'm only focusing on paizo sources right now), but I'm not sure if poison would count as an energy type, and I'm pretty sure piercing wouldn't.

The obvious answer would be "Just don't use those dragons as your patron", but if I was going to accept that, I'd probably not be posting it here.

Would these dragons be legal to use as patrons, and would a Dragon Herald get con damage resistance or piercing resistance, respectively?

Answer 1

Ultimately this is up to your GM but if one of my players came to me with this I would give them the following:

(Imperial) Forest dragon

Coat of Arms (Ex): piercing, while not really an energy the dragon itself has DR/Adamantine so it has a thick skin and that would be a bit much for a pc for an archetype having effectively DR that everything but piercing goes through would not be game breaking and as levels go on and more and more magical effects happen this will fall behind in effectiveness compared to the regular energy resists

Rebuke Foes (Su): piercing, similar to the above this will likely have a lesser effect as time goes on and things have more DR it will be weaker against as it would not break DR like most energy damage does. However, against things that have energy resistance to everything this will be very effective against as most of those do not have a high DR to go with their energy resistances.

Guardian Dragon

Coat of Arms (Ex): bonus to save vs poison, since the guardian dragon does its con damage by way of poison

Rebuke Foes (Su): this is more difficult as if you took the Breathe Weapon and converted it directly that would be 24 Con Damage per round and that would be more than a little broken. So in this case I would give you the "Agonizing Venom" ability with no damage and the DC set as the standard extraordinary ability using charisma as the stat DC 10 + 1/2 level + ability modifier