The Flight to Lucifer by Harold Bloom

That night, Olam and Valentinus had gone separate ways, agreeing to meet at midnight later, when they would depart from Lucifer. Valentinus marched around the western edge of the lake, while Olam followed the eastern path to the tower, at the lake's northern edge.

Olam grunted as he went by the huge stone wall, and he spared a single snort for the black rock.