Dark Souls is extremely funny when you consider that item describtions don't exist in-universe
There's like a hundred different rings and they all do different things and the only reason why you know what they do is because the game actually tells you.
But in-universe, the Chosen Undead somehow made the call that putting on the ring with the little orange stone from it that dropped from the horrible big demon monster is going to enable them to walk on lava. Like, what's the thought process here? A ring that appeared with such convenient timing couldn't serve any other purpose?
I can excuse the Covenant of Artorias because the Chosen Undead may actually have known about Artorias and therefore deduced that a ring found at the grave of a man known as the Abyss Walker might be helpful for not getting consumed by the Abyss (though even then, it's a 50/50 choice because you also find the Hornet Ring there), but a random fire demon having a ring of lava walking would be far less expected.
Or you find a random ugly little doll in the Undead Asylum and that will for some reason step inside a painting in Anor Londo.
It's absolute insanty if you really think about it.
