Amarthiel (Sindarin for Daughter of Doom) was an important figure during the Battle of Fornost. She was slain by the Elf-maiden Narmeleth during the Battle of Fornost, and her spirit wandered around Middle-Earth for two-thousand years until she possessed the one who slew her and attempted to search for Narchuil, a lesser ring that once belonged to her. She took on the guise of the deceased Sara Oakheart to fool the player, until her true identity was revealed. She would later fool players once again by taking on the role of a Lossoth wise-woman, Saija. She used this disguise as a means to keep an eye on her champion, Mordrambor, of whom she suspected of treachery. She was in the end slain by Mordrambor and the Witch-king, the hand that bore Narchuil cut from her.
Amarthiel appears in the following Epic quest instances and locations; at some occasions she engages in combat:
-  Volume I, Book 9, Instance: Oakheart's Might — Barad Gúlaran in Angmar
-  Volume I, Book 9, Instance: Amarthiel's Hope — Annúminas in Evendim
-  Volume I, Book 10, Instance: The Eye of Angmar — Barad Tironn in Evendim
-  Volume I, Book 13, Instance: The Path of Aearil — Halla-kolo in Forochel
-  Volume I, Book 14, Instance: The Prisoner of Sammath Baul — Sammath Baul in Angmar
-  Volume I, Book 14, Instance: The Fate of Laerdan — Tham Mírdain in Eregion
-  Volume I, Book 14, Instance: The Doom of the North — Tham Mírdain in Eregion
- It is unlikely that Amarthiel could have merely been of the Race of Man, as her spirit continued to exist in Middle-earth even after her death. It is most likely she was one of the corrupted Maiar who fell under Morgoth's sway.
- A post by MadeOfLions on 15 January 2015 explains:
Amarthiel is indeed exclusive to LOTRO - you won't find her in Tolkien's works, though the inspiration for her comes from here and there throughout. We had lengthy meetings back in the day to work out her story and bring her to life, names you'd probably recognize if you've been here since the beginning: Keth, NobOrBob, Berephon, and myself on the story side, and Floon with the art. Amlug even contributed a crucial book of the Epic (Volume I, Book 9 - which gave us some particularly flashy Amarthiel moments). I wouldn't say we pulled her out of a magic hat, though. The themes that revolve around Amarthiel are very much in tune with Lord of the Rings, I think. MoL