Doesn't she look familiar to you?
The Most Faithful Mirror is a deathknight sworn to the Walker in Darkness, most often seen wearing a full suit of heavy soulsteel armor and carrying a grand daiklave of the same material. She does not appear to have the power to speak, and while she seems polite and deferential, is a terrifyingly powerful opponent.
Under her armor, she is a slim muscled young woman with white hair and dark eyes, her pale skin marred by scars and old wounds, with a horrible unhealing gash across her throat.
She is always seen with her partner/handler, The Violet Harbinger of Horrors Best Unknown.