Being a Revenant of the Dead King meant that she was exceptionally powerful to have survived the future incursions of the Dead King as well as to be in charge of watching over the Woe. Despite this power, she has been repeatedly thwarted by the band as well as making fatal mistakes due to the revenant's pride.
Thief of Stars is implied to have gone for objects very hard or impressive to steal. This brought the known revenant to her downfall as she tried to rob The Silent Palace from the Dead King, and was made it's guardian after her death.
An inherent ability is being able to meld and camouflage their presence to both visual and magical means. The Thief of Stars also possess the ability to steal things and as shown when drawn on by Hanno escape bindings. The Thief of Stars is able to pull constellations from a hidden space and the constellations can, in turn, cause an effect over a widespread area.