Dalamar
Adventurer
Think of it this way: All the MM dragons gain an immunity to the energy that their breath weapon uses (I'm pretty sure all true dragons do). When you suddenly have a dragon that has vulnerability to the energy its breath weapon uses, it just seems very out of place.
It seems to me that it's a stable part of DnD that if you have a monster that uses a certain energy/element excessively, it has immunity or resistance to it. Look at the balor: it has Immune to Fire instead of the standard Resistance to Fire 10 that all Tanar'ri have since its image includes fires over and beyond that of the other demons.
It seems to me that it's a stable part of DnD that if you have a monster that uses a certain energy/element excessively, it has immunity or resistance to it. Look at the balor: it has Immune to Fire instead of the standard Resistance to Fire 10 that all Tanar'ri have since its image includes fires over and beyond that of the other demons.