“The once-thriving town of Orcrest may be the location in Northern Elsweyr that was hardest hit by the Knahaten Flu and the breakdown of society that followed. Abandoned and haunted by its own dead, Orcrest is now a place of dread for the nearby surviving Khajiit.”
This is one of the best hidden skyshards in Elsweyr. You really need to rely on the clues from the title, and to think a bit outside of the box. The first part of the sentence, “In the darkest depths”, is the key to everything. It points toward the fact that this one is found at some lower, underground part of Orcrest.
The entrance to the area where all the pipes converge is called the Sewer Access. As you find yourself at the gates of Orcrest, continue forward but keep to your right. Go to the left of the pathway with a broken-wheeled cart. You’ll pass by an orange cart on your right, and a green bush on your left. This is where you turn left, toward a part of a building wall that is a bit wider than the rest, with a vine coming down from the top. The wooden doors of the Sewer Access are here at the bottom.
Once in the area of the darkest Orcrest depths, continue forward toward the central part. If you look around, you’ll spot a lot of pipes converging at the center of the room. When you come close to the edge, you’ll spot the shard’s glow at the bottom of the hole.