She is very loyal to her family, as she read the story of her father's past and was fascinated by the details. She believes her father is truly the savior of humanity and calls it an honor to fight by his side. She cared for her sister Olympia Savage and was devastated by her death but made sure she was honored with a worthy funeral.
In spite of her strong will, she has a vulnerable side to her. She was horrified at witnessing her father killing her sister, as a form of mercy to end her suffering and stuttered to justify it. She also told Deathstroke of knowing not to be attached to things.
Cassandra was onboard the Warworld as Vandal confronted the incoming armada and declared that Earth was off-limits to all incursion or invasion. Cassandra was asked by her sister if she read the part of the bear battle, before telling her to hush as their father battled the armada. Cassandra soon had Olympia alert Vandal that another armada was incoming from the other side of the solar system, so Savage realized that it was someone who knew that the Warworld couldn't be in two places at once. She watched as Vandal contacted Darkseid to ask for resources to help and his partner acquiesced the request was sent in by Olympia.
Darkseid deployed his son Kalibak, who then annihilated the entire one of the armadas by sacrificing one meta-human. Savage noticed that one alien had a star creature brethren latched to his face and realized how he could win the battle. Once Vandal realized what they were facing, he turned the control of the Warworld over to Cassandra, who was taught how to use the base before she detected another ship scurried away in the darkness of space, behind the armada.
After the battle, Cassandra watched as her father put the remains of Starro in the holding cells of the Warworld. She expressed her enjoyment at fighting by his side and calling him a true savior. Not long after, Olympia once more brought up the battle with the bear and her intentions of putting her new favorite moment of watching the battle in space in the book. Cassandra watched as Vandal denied her request and soon hugged his child before snapping her neck, killing her. Horrified, Cassandra nervously justified his act as a humane way because of Olympia's deteriorating mind and ending her pain. Cassandra declared that she would make the proper arrangements for the funeral, as Vandal told her to make it one worthy of her.
Vandal Savage has had many children in the comics, but Cassandra was created for CW's DC's Legends of Tomorrow. Appearing in the season one episode "Leviathan" played by Jessica Sipos, Cassandra is a loyal lieutenant in her father's quest for world domination who turns to the resistance after she learns he was responsible for the death of her mother.