MarkB
Legend
My headcanon for the One Ring and invisibility was that it basically required some advanced knowledge of Ring lore to specify its effect, and the last wielder to possess such knowledge was Isildur. He set it to "invisibility" mode, and no subsequent wearer knew how to switch it out of that mode.That's how they ended up working at the ultimate end. But they were made to enhance what the wearers desired. The dwarves wanted to mine and own things, so it made them better at achieving great wealth, and made the wearers greedy. The humans wanted power, so it gave it to them and then corrupted them into the Nazgul.