Kassandra (458 BCE – 2018 CE), also known as the Eagle Bearer was a Spartan mercenary who fought during the Peloponnesian War.

She was the older half-sister of Alexios and,through her mother,Myrrine,the granddaughter of King Leonidas I of Sparta.Although raised by her step-father,Nikolaos,Kassandra was the biological daughter of Pythagoras.She was also the mother of Elpidios,an ancestor of Aya,one of the co-founders of the Hidden Ones.

Kassandra was born in Sparta to Myrrine,the daughter of the late King Leonidas I and the philosopher Pythagoras,whose lifespan was extended due to the Staff of Hermes Trismegistus he possessed. Shortly after her birth, her father departed from Sparta on a quest to learn more about the Isu and the staff he possessed. As such, Myrrine was left to raise Kassandra alone. As a baby, Myrrine brought Kassandra to the acting Pythia, who proclaimed that the child showed a lot of promise.At one point, Myrrine later met and married the Spartan general Nikolaos who, despite Kassandra not being her own flesh and blood, raised her as one of his own. Kassandra would later gain a younger brother, Alexios.

Owing to her lineage as being a granddaughter of Leonidas, great hopes were placed upon her to live up to the strength and valor of Leonidas.As such Kassandra was trained to fight at a young age by Nikolaos.While training in the woods near Sparta as a child, Kassandra was presented with the broken Spear of Leonidas, an Isu weapon, as an heirloom by her mother. Afterwards, Kassandra wouldn't let go of the spear, even in her sleep, telling her parents that she needed it "to fight the monsters in [her] dreams."

During her mercenary travels, Kassandra came into conflict with the secretive Cult of Kosmos, an organization intent on controlling the entire Greek world. She later opposed the Order of the Ancients, who sought to hunt her down, due in part to her nature as a Tainted One, and also for her allying herself with Darius. For her opposition against the Cult and the Order, Kassandra is considered one of the early precursors to the Assassin Brotherhood.