Delirium is the youngest of the Endless.
She smells of sweat, sour wines, late nights, old leather.
Her realm is close, and can be visited; however human minds were not made to comprehend her domain, and those few who have made the journey have been incapable of reporting back more than the tiniest fragments…
Her appearance is the most variable of the Endless, who, at best, are ideas cloaked in the semblance of flesh. Her shadow’s shape and outline has no relationship to that of any body she wears, and it is tangible, like old velvet.
Some say the tragedy of Delirium is her knowledge that, despite being older than suns, older than gods, she is forever the youngest of the Endless, who do not measure time as we measure time, or see the worlds through mortal eyes.
Others deny this, and say that Delirium has no tragedy, but here they speak without reflection.
For Delirium was once Delight. And although that was long ago now, even today her eyes are badly matched: one eye is a vivid emerald green, spattered with silver flecks that move; the other eye is vein blue.
Who knows what Delirium sees, though her mismatched eyes?"
The Sandman: Seasons of Mist, Episode 0, Issue 21 (1990), by Neil Gaiman
The tragedy of Delirium is… she is forever the youngest…
… For Delirium was once Delight…