What is dragonfire like in your books/worlds? It can behave in wildly different ways depending on the setting. In my setting, dragonfire burns hotter than the sun. It behaves like napalm, sticking to whatever it hits, but has the weight and force to carve out tunnels. Anyone unlucky enough to be caught in the blast is obliterated, those not in the path of the flames will often die of the caustic vapors eroding lungs and flesh. A city hit by dragonfire resembles nothing more than a nuclear strike zone. It’s produced by a dragon’s blood equivalent detonating in the throat like a multi-stage rocket, accompanied by a deafening series of shockwaves. Even dragons aren’t entirely immune to their flames, and it’s possible to kill or scar one with enough time.
The dragons in my Draconia books have a pair of air sacs above their lungs that, when the dragon breathes into them, super heats the air, recycling body waste that would be excreted in young dragons and other creatures. When exhaled, this super-heated air mixes with a special saliva produced at the back of the throat, producing a fireball. They can either release one powerful fireball (powerful enough to reduce as small spacecraft to a burnt-out shell) or, with practice, release a volley of smaller fireballs. When used on other creatures, the fire can fuse bones at the point of impact.
An elemental blast of fire that ignores durability, if that makes sense. Under it's influence, stone, metal, plastic... all run like water, even though it shouldn't be possible at the temperature it is recorded at. Certainly enough to kill any human it hits... but not to the point that solid granite liquifies like that. And it is impossible, because it is evidently a world-warping attack. The attack itself not only gives enough heat to melt most things, but also reduces the melting point of anything it srikes, by way of directly affecting the laws of physics.
I still have not figured it out entirely, but in my setting dragons would likely be demonic beings and would breathe fire hot enough to melt stone, at the very least. And yes, fire will actually be napalm-like liquid that is not only flammable, but also corrosive and/or toxic, meaning that effects are actually very similar to what you have described for your dragons.
I haven't decided if I want to include dragons in my stories. But of I do I'm thinking of them being more connected with poison and acid than fire. I like the idea of dragons breathing out burning liquid as opposed to "only" flames.
Hope this is okay since it's not dragons, but in my current story there is a Phoenix, and the element of "Phoenix-fire" is associated with it and the main character. The Phoenix is basically a god, so there's a whole religion created around it, and in the main temple in the country there is a brazier of this Phoenix-fire at its altar, which is also called the "Eternal Flame". The major features of Phoenix-fire are: 1.) Does not produce smoke. 2.) Shifts between a rainbow of colors, not just red, orange, yellow, and white. 3.) Is said to have come from the sun, since the Phoenix is said to be born from the sun. 4.) Can harm or heal depending upon the intention. 5.) In the case of the main temple's altar, the fire will never die unless the Phoenix itself dies.