The entrance to the Tomb of Valor is located on level 2 of Stormhold. As you enter you are greeted by the ghostly apparitions of the Knights of Thunder. They are harmless and will walk through you, eventually despawning when they reach the back wall.
The Tomb of Valor is a gauntlet that requires you to shut the various sarcophagi that line the walls of the tomb while fighting zombies. Once all the sacrophagi have been sealed, Lord Chesgard, a former hero of the Knights of Thunder will spawn at the western end on the instance.
To start the gauntlet, interact with the sarcophagus to your right as you zone, located at: ( 2, -46, -48 ) /waypoint 2, -46, -48. A restless stormlord will slowly creep out. Upon it's death, the other sarcophagi will open, releasing the zombies within. In order to close a sarcophagus, you must first slay the restless stormlord that crawled out of it. Do this for every sarcophagus. The catch is that in order to spawn the boss, all the sarcophagi must be closed, but ones that you formerly sealed may re-open at any given moment. Just be quick about closing them and you should have no trouble with getting them all to be shut at the same time.
Once Lord Chesguard has been dealt with you can leave at a grate on the ceiling at: ( -5, -46, -47 ) /waypoint -5, -46, -47