The first story in the Assassin Prime series by Scott Moon
(Originally published in the Explorations: War anthology)
The Hand of Empyrean introduces Pyr, an immortal assassin, who made a devil's bargain to save her people thousands of years ago. She has a new mission now, but never realized what meeting a young woman from her home world would mean to her destiny.
Pyr kills without mercy, fights without a fear, and must decide kill Eva, free her, or doom her to a life fleeing the astral warriors of Empyrean.
Please check out this 43 page short story and leave a review if you'd like to see more in this series.