The entrance of this delve is not your typical front door. Someone actually build a tower on top of it. In order to enter, find this tower and a hatch on its ground floor. It is a passage inside the delve. If you are a fan of a spell spell critical and spell damage gear, be sure to check out the nearby Boreal Forge to the east. You can craft Law of Julianos set here, with a favor toward the spell caster traits.
From the entrance head north. Find a small passage that conects first larger cave room, with the one on north. Go through it and now keep toward your right. In the corner of this room, there is a small staircase that takes you toward the eastern side of the dungeon. Once you are on it, head south. Careful not to drop down from here, as it is required to re-do the route again if you want to return. The shard in this spot, is protected by a crumbling gargoyle, hence the name I suppose.
Sand Kingdom Moons - Super Mario Odyssey Power Moons