Therdis has the dark hair and blue-gray eyes common among the Dúnedain. Taller than the average Man and indeed standing more than a head above even many men of her own people, she has the awkward, gangly-legged stance of a shore-piper or heron. Her habit of standing motionless in some awkward position does not help this comparison. From behind or with her face obscured, it is easy to take her build for that of a very lean, long-haired man. Even among a people known for their strong, dark features, she is best described as 'angular' or 'harsh' rather than beautiful or even striking. She smiles rarely, and when she does, the expression is often unsettling rather than reassuring. Her voice is low, and painfully hoarse, as one who has inhaled something damaging or caustic.

She dresses in shades of gray. When traveling, she is armed with a plain one-handed sword and a dagger of similarly utilitarian make. She is a capable swordswoman, though her form lacks any natural grace or elegance and was earned instead through hours of tedium. After her return from disappearance during the War, she occasionally carries a simple crossbow of Angmarim make. 

Those meeting her for the first time are usually struck by her distinct lack of conversational skills and odd body-language mannerisms. Either seeming entirely distant or assuming far too piercing a stare, she is generally considered unnerving at best and threatening at worst. As such, the woman claims few among her own people as true friends, though she makes friendly acquaintances easily with children and young people who are less likely to assume aloofness from a first impression.