It was sheer pleasure, hunting, knowing that if he did not find food he would not eat, learning to move even more silently through the Underdark than before. He could smell water, feel the subtle change of humidity before the drop and laugh of a stream reached his ears, and it was rare indeed that his waterskin or his stomach were left empty. And all the while he considered, plotting revenge, how to finish his business with house Slyan'ssun so that he could leave it behind forever. He stayed a goodly distance away, roaming the uncharted ways toward the haunts of the dwarves and the other denizens of the Underworld.
Time passed, blurring out of measure in the lightless Underdark, the division of day and night merely functional, serving no purpose to him. He woke and hunted when he was hungry, explored the realms of subtle beauty and overawing grandeur at his leisure, and slept lightly when he felt the need. Drow do not dream, although they sleep, their heritage from their distant cousins the surface elves; but he found slowly as the trackless days and nights slipped by that something like dreams began to afflict him. They came in the moments between sleep and waking, after his eyes closed and before he could bring himself completely awake, came and lingered in his mind until he drove himself even harder, trying to escape them.
There was a forest, of the kind he had seen only in his rare raiding excursions to the surface, trees thick and shadowed, glowing with their own faint phosphorescence as ghostly figures moved through them. The black, moonless sky was illuminated only by a single star, its light pooling down into a clearing in the forest, refracting from a haze of fog, concealing the clearing's contents.
Around it, the ghostly figures passed, dwarves and elves and men and drow, moving with solemnity and purpose as they carried out their pointless tasks. Their garb and the specificities of their purposeless rites changed from vision to vision, but they were always vain and empty, performed in the utmost seriousness despite the uselessness of the actions. And always, they avoided the clearing, their motions carried out in the forests surrounding it, their eyes averted from its glow at all times.
He found himself profoundly disturbed by the visions, and adopted a practise of making himself work until he was utterly exhausted before tucking himself into a relatively safe corner to sleep. It didn't help. Nothing did, until the day he found himself unexpectedly in sight of the walls of a drow city, a far detour from the place he thought he'd been. Too exhausted to keep going that day and resolving to turn around and go the other way - back to the unpopulated parts of the Underdark - as soon as he woke, he concealed himself in a ledge-top crevice to sleep.
The visions, he found that night, had gone.