A willing creature you touch shape-shifts, along with everything it’s wearing and carrying, into a misty cloud for the duration.

While in this form, the target can enter and occupy the space of another creature. […] can pass through small holes, narrow openings, and even mere cracks, though it treats liquids as though they were solid surfaces.

This is one of the few transmutation and movement spells that don’t require you to end your turn or movement on an unoccupied 5ft square.

This should work. Nice!

Doesn’t say anything about not needing to roll stealth checks, or the transmuted armour not causing disadvantage on those checks.

That’s a silly argument.

I believe that’s called a ‘holy hand grenade’ by the long-ago people.

What is DnD other than an engine to start silly arguments?

Hold on hold on…

Are there any rules about the mass of the Gaseous Form?

In the absence of a rule that specifies “reduced total mass” as part of the Magic effect, I would assume normal rules of reality apply.

As such, the same number of moles that previously comprised the Paladin and Dragon are now gaseous species at local temperature & pressure. That’s the magic, yaay!

But it’s the same number of protons, so it’s gonna be just as heavy. Even if you can squeeze all those molecules into a small-ish container, it’s gonna have the weight of the paladin, his armor, and his dragon.

It might have the same mass, but considering they gain a fly speed, their (effective) weight is zero.

If there are in a sealed container that wouldn’t matter, unless it flies using a magical force without an equal and opposite force, at which point you might as well just throw out conservation of mass.

Mr. Martin Fart-in-a-Jar, the Paladin.

No summoning sickness? LPT fr.

I think the spell represents sublimation, which doesn’t convert mass to energy (actually requiring energy, but I guess that’s the “magic” part of the spell). So the paladin’s mass (body, armor, weapons, etc.) would remain. I’m not sure how to decide how big the bottle needs to be (though, likely not very large), I just don’t know how the party is reasonably throwing the bottle. It’s similar to picking up the paladin (in their normal, physical form) and trying to throw them across the room.

Sir Molotov of Cocktail.

I’m part of a Western Reaches campaign where I’ve got an entire party worth of characters to pick from. In here are two with the Fey Touched feat, giving them the spell Misty Step, this being a warlock and a paladin. While the former would use that to get out of hairy situations, the latter would use it to get into them.

So basically I also have an option for a sudden, in-your-face paladin.

Buoyancy. It has weight, but if it’s lighter than air, it still floats.

For it to be buoyant, density would have to be less than air. If we’re holding to conservation of mass, then the bottle would have to be significantly larger than the paladin, which doesn’t sound particularly stealthy.