The Great Rings

A mortal, Frodo, who keeps one of the Great Rings does not die, but he does not grow or obtain more life, he merely continues, until at last every minute is a weariness. And if he often uses the Ring to make himself invisible, he fades: he becomes in the end invisible permanently and walks in the twilight under the eye of the dark power that rules the Rings. Yes, sooner or later --- later, if he is strong or well-meaning to begin with, but neither strength nor good purpose will last --- sooner or later the dark power will devour him.

No veil between me and the wheel of fire

"Do you remember that bit of rabbit, Mr. Frodo?" he said. "And our place under the warm bank in Captain Faramir's country, the day I saw an oliphaunt?"

"No, I am afraid not, Sam," said Frodo. "At least, I know that such things happened, but I cannot see them. No taste of food, no feel of water, no sound of wind, no memory of tree or grass or flower, no image of moon or star are left to me. I am naked in the dark, Sam, and there is no veil between me and the wheel of fire. I begin to see it even with my waking eyes, and all else fades."
-- J.R.R. Tolkien, The Return of the King