Kain Darkwind wrote:
If hp is non-serious damage, what does loss of hp from acid and lava entail? Someone who just isn't really harmed by the lava?
Probably. Anyone who survives the first round is clearly beyond an ordinary human. Especially considering that by the rules simply losing hit points is its own punishment, so a PC that survives this wouldn't even suffer anything beyond superficial scarring: no loss of senses or limbs or anything. Anakin Skywalker was clearly an NPC.
Of course, Sir Galahad never fell into lava to the best of my knowledge, so we really don't have a guide as to whether this is heroic or just absurd.
That said, it would seem from videos that first one smacks into the surface of lava like a really really hot rock. Then you catch fire, and the released gases start agitating the surface and you may start to sink.
Relevant to this topic are the damage values suggested in the 5e DMG. They have tumbling into a fire pit at 2d10 damage, submerged in acid vat at 4d10 damage, wading through lava at 10d10, and being submerged in magma at 18d10. Incidentally falling into a vortex of fire on the Elemental Plane of Fire is rated at 24d10.