To reach the dungeon entrance, you’ll need to come from the north. This entrance is on a higher plateau, with an ascending path, coming from the north. As you climb up, keep to your right, and soon enough, you’ll reach a portal. Use this portal to enter the delve.
“The Withering Hermit says the Shadow Cleft is just a gloom-dusk cast by Nocturnal’s Evergloam, whispered the voice from the darkness. “But her wandering star fell long, long ago.”
As you enter the dungeon, open up the map. You’ll spot a long river running through its center. Your goal is to reach its eastern end. There are not a lot of enemies on your path there, and they even come in small groups. This is good, because you can simply run in there, without any fear. At the end of this river, there is a large waterfall. Be careful while jumping down there, because it is a bit high. There is actually a piece of deeper water you can safely land in, but you can miss it completely.
The Shadow Cleft Skyshard is down the waterfall, in the center of the small cave room with a couple of shiny wafts, making it a mystical and unique experience.
Shadow Cleft Entrance
Amidst the wafts in the Shadow Cleft.
Sand Kingdom Moons - Super Mario Odyssey Power Moons