What does this information mean?
This quest takes place in an instance of the D'Morte Burial Chambers called Acquisition, and in The Crypt of T'haen: Endless Twilight instance. (The Epic x 4 raid zone called The Crypt of T'Haen: Vengeance does not give an update for this quest as T'Haen the Lost kills T'Rath the Usurper who is needed to complete this quest).
You must have completed enough of the Bloodlines Chronicles
Timber Falls Quest Series to gain access to The Crypt of T'haen. Completing the quest Shattering the Crystals (Good aligned) or Exploring the Crypt (Evil aligned) grants access to The Crypt of T'haen.
Visit Soul Eater Falls in Nektulos Forest. ( 501, 28, -1540 ) /waypoint 501, 28, -1540
Return to the D'Morte Burial Chambers and enter the Acquisition instance.
Kill Izinar Malkevantrii ( -5, -4, 74 ) /waypoint -5, -4, 74 and his two assistant conjurers. You will receive a new Crest of D'Morte, and your old one will be destroyed.
Note: He will attack even if he's a grey con to you.
Return to Soul Eater Falls.
If you have not already done so, begin one of the Bloodline Chronicles series of quests Missing Scouts (good) or A Small Sampling (evil) and continue with the quest series until you receive access to The Crypt of T'haen via Shattering the Crystals or Exploring the Crypt.
Enter The Crypt of T'haen.
Find and destroy from which it is said that A Magnificent Coffin Dryxl T'Rath receives his power. It is at ( 94, 56, -66 ) /waypoint 94, 56, -66 off one of the small ramps from the platform where you find T'Rath the Usurper.
Destroying the coffin is optional but if you don't destroy the coffin he starts healing at 35%.
To reach the coffin go to the narrow bridge at loc (0, 57, -59) and cross the chasm. Take a left then follow the path to the room with dozens of coffins.
Destroy Dryxl T'Rath (known as T'Rath the Usurper) ( -7, 61, -26 ) /waypoint -7, 61, -26. You will receive a new Crest of D'Morte, and your old one will be destroyed.
Note: This last step, is identical to the quest A Vicious Twist (Hand of Marr series) or Crushing Betrayal Brethren of Night series). Consider doing at the same time.