Search for tomb off the southern coast of The Thundering Steppes. Take the griffin to Coldwind station. The tomb is literally just off the beach at Coldwind Cove, underwater ( 394, -79, 1437 ) /waypoint 394, -79, 1437. You can use the griffon tower as a landmark, head into the water and slightly right of it. There are Rallosian ghosts around the tomb.
Search the bags around the tomb on the seafloor by clicking the bags.
Seek out the Unkempt Druids at ( -692, 12, 552 ) /waypoint -692, 12, 552 near the Ruins of Karana in the The Thundering Steppes. They're up on the rock wall. More specifically, just North of Varsoon. You can take the South East griffon station to get close.
Speak to the druid leader, Eilwyn Loamskin. You must persuade her to give you the key that opens the tomb. Once she agrees, you'll find the key in one of the boxes on the ground near her. The fanatical rangers at the campfire are aggro. I was able to speak to Eilwyn while invisible, but was attacked by the rangers as soon as I opened the box to take the key. If aggro gets too much, kill one, run, come back and "Finish It"...lol.
Head back to the tomb, open it up to get the shard. This takes two examinations of the tomb.