You will find the tomb in the Underfoot Cathedral at 1, 28, -410
A group of three heroic aerakyns level 103 will spawn and attack you. Kill them.
Search the Tomb of Orisin Deepwell. Click the tomb where Neragul was standing.
Track down Neragul, and retrieve the key!
Kill Neragul in his normal location in Halls of the Betrayer (Heroic), you will receive a letter. Examine the letter.
Find Neragul's Cache.
in the middle room where Grendish is located. Kill room as normal and have Grendish fly off. Near Grendish balcony, there is a large square on the wall and glowing in the middle, click this for the cache.
Return to Loremaster Dorondal at 472, -208, 275 in Thurgadin .