WoWDB

This item unlocks the hidden corruption called Corrupted Remembrance for the Retribution artifact,  Ashbringer.

From MMO-Champion:

The entire process is a reference to a post from ten years ago investigating the Ashbringer.

 

• Make a copy of A Complete Copy of "Nat Pagle's Guide to Extreme Anglin'.":
• Head to Dire Maul and loot  A Thoroughly Read Copy of "Nat Pagle's Guide to Extreme Anglin'." from A Dusty Tome
• Head to Alterac Valley and loot Nat Pagle's Guide to Extreme Anglin' from player corpses.
• Somehow convince Sister Elda to combine the parts. (Update: This appears to be tied to Artifact Knowledge level.)
• Kill Nefarian for Head of Nefarian
• Bring these items to Prince Tortheldrin and turn it in.
• Head to the Bulwark in Tirisfal Glades and talk to the traveler who talks about Timolain.
• The Traveler will send you to find Grand Inquisitor Isillien's Journal an  read it.
• Get Timolain's Phylactery by killing a slime.
• Summon Timolain and fish up the Shard of Darkness from the Thondroril River.

Return to Lord Maxwell Tyrosus in your order hall and the final quest, Walking in Shadows, rewards the appearance.