Philonoe

Philonoe (Φιλονόη) - A Spartan princess who was granted immortality by Artemis, with the help of Hades, when she had suffered a tragic death far too young in a mortal’s life. Being one of Artemis’ closest companions, she and the rest of her allies could not bear the loss, and she sought out Hades to restore life to Philonoe, who had become a shade.

Hades succeeded in giving Philonoe her humanity back, though she kept the blue hue that all shades carried. Still, she serves and is close friends with Artemis.