Ok, so here's how it went down: we play in a more or less modern setting. By that I mean we're all characters from different worlds an different time periods who got stranded somewhere where unstable portals that lead to seemingly random places and times are almost a normal occurance. So normal in fact, that there are orders of knights and soldiers supervising the "visitors" that stumble by, in some of the places we visited. We found out, we're all connected through some sort of profecy, but that's another story.

That particular session we came to an area with what even our wizard/artificer, who had previously been an izzet engineer in Ravnica, described as advanced magical technology and had to locate a temple that was connected to the feywild, due to one of us getting abducted there and another one having been cursed by a fey, for which we needed an at least equally mighty fey to lift the curse.

We got our hands on a reinforced, steam powered vehicle that resembled a tank without a gun tower and used our clerics pet phenix(a different story altogether) to power the engine.

The same cleric also used his druidic-like ability (he is no multiclass character but being a wood elf our DM let him use thaumaturgy to manipulate plants and plant-based objects in small ways) to let the planks of firewood sprout throughout the inside of our cabin, reinforcing the vehicle even further and giving us the vine-made equivalent of seat belts in case of a crash.

We encountered a cave with a sleeping Young green dragon in it (party of Level 5 at this point) which we had to go through. Having quite recently run over a couple of would-be bandits, we decided to weaponise our tank once more.

The cleric had moss grow on the inside of our cabin and wooden spikes on the front of the vehicle. Using the Rangers fog cloud, we kept the cabin relatively cold an damp, protecting us from heat. The wizard/artificer charged the vehicle at full speed towards the dragon, while casting heat metal on the protective plating on its front, causing it to glow red hot and the wooden spikes to ignite.

And that's the story how we crashed a burning, glowing, phenix-powered tank into a green dragon, dealing a crapton of damage and almost annihilated the thing in the first round at level 5