Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: The Elder Scrolls III: Morrowind
Dagoth Ur is literally nightmare fuel, he is a Mad Dreamer who gives Bad Dreams to people. Here's a quick example:
I AM THE SHARMAT I AM OLDER THAN MUSIC WHAT I BRING IS LIGHT WHAT I BRING IS A STAR WHAT I BRING IS AN ANCIENT SEA WHEN YOU SLEEP YOU SEE ME DANCING AT THE CORE IT IS NOT A BLIGHT IT IS MY HOUSE I PUT A STAR INTO THE WORLD'S MOUTH TO MURDER IT TEAR DOWN THE PYLONS MY BLIND FISH SWIM IN THE NEW PHLOGISTON TEAR DOWN THE PYLONS MY DEAF MOONS SING AND BURN AND ORBIT ME I AM OLDER THAN MUSIC WHAT I BRING IS LIGHT WHAT I BRING IS A STAR WHAT I BRING IS AN ANCIENT SEA