Bia

Bia is an Olympian Goddess and the personification of Force and Raw Energy, daughter of Zeus and Styx, and sister of Nike, Kratos, and Zelus.

She is one of the Four Divine Lords, technically the only Divine Lady, serving the goals of and protecting the Grand Lord: Zagreus.

As one of the Grand Lord's highest warriors, and his personal protector, she wields the Holy Sword Fotismos that contains power on the Protogenoi Aether's level.

Mythical Age
Along with her mother and her siblings she was noted for her allegiance to Zeus during his War with the Titans, she however became tired of the very little action that serving Zeus broke and along with her two remaining siblings, left Zeus's service to join Zagreus as Nike before had joined with Athena.

Pre-/During The Last Olympian
Bia followed Zagreus in his support, and the support of Zagreus's two Underworld sisters, in aiding the Titans rise to power. When Kronos was defeated, Zagreus took his followers and sisters to ground, hiding aboard the Ark.

Trivia

 * Bia is a Daughter of Zeus, and her brothers are his sons, a common running theme in Greek myth is Zeus's many love affairs.