Tombs of the Na-Totambu is the dungeon hiding this skyshard and it can be found in southwestern Craglorn.
You can approach the hidden entrance of this dungeon from north. There is a small bridge southeast of a nearby wayshrine, that you need to walk over in order to reach Tombs of the Na-Totambu entrance. As soon as you enter the dungeon, you can look to your left and spot the shard. In order to collect it you need to reach the very end of the dungeon. Soloing your way toward the shard is hard, and you are likely to get killed couple of times if you try to do so (that is if you do not play as a stealthy nightblade). Shard is at the end of a small tunnel, just behind the dungeon boss – The Hungry Pillar.
Bridge that leads to Tombs of the Na-Totambu entrance.
Tombs of the Na-Totambu Entrance.
Tombs of the Na-Totambu Entrance Map Location.