The Blackscale Sepulcher  

Boss is a three mob encounter - Grash lvl 69^^^ with friends Tival (lvl 69^^) and Timant (lvl 69^)
To spawn the boss encounter, you must kill the placeholders surrounding the pit on four sides. Placeholders could be any of the following mobs: Blackscale Plague Bearer, Blackscale Firebrand, and Blackscale Razorwing. The mob types is not important and they will change to a different mob of the previous list approx every minute. The goal here is to kill placeholders until A Steward is standing in every spot. A steward will not pop everytime you kill a placeholder though so this can be aggravating. For best results:

Have your group stand in the middle of the pit. (there's a rock structure there you can walk up on.) Pull all four placeholders at once insuring that all are killed at relatively the same time. Wait for respawn. Sometimes you will get for example 2 stewards and 2 more placeholders. Rinse and repeat the above method until stewards are all around. Once all stewards are up, pull them all at once. After they've been killed. The boss encounter will spawn immediately. Be prepared for them.

Strategy Tips courtesy of Kryptos Dracul and Faraday of "Order of the Ravenclaw" Najena server.