Leiko is the only daughter of businessman Daichi Tanaka and professor of archeology Noriko Tanaka; her two brothers died of overdose before she was 15 years old. After her mother's brain was damaged for attempting to interface with the Core, Leiko grew under the influence of the alien device and the harsh ubringing of her father. Discovering that the Heart Of The Universe was in possession of Bob Null and that the only way to activate it was by being pregnant, she conceived the child that would one day grow to be Noriko Null. Leiko was recruited in the Mortal Liberation Front and acted as their secret agent on Earth; Noriko grew up without knowing the identity of her mother.
After Leiko revealed herself to Noriko 18 years later, Athena activated the Nexus that the Mortal Liberation Front had installed into her brain during the pregnancy. Mother and daughter would soon start a bitter rivalry, leading to the Scion Corporation takeover by Null Technologies. Later, by using technology stolen from Noriko and with the Core's help, Leiko founded the terrorist organization called the Empire of Shadows and used the identity of Empress of Shadows. Leiko has also formed secret alliances with Hermes, Eris, the Scribe and the Mist.
During the Guild invasion of Earth, Leiko was almost able to conquer the entire planet and steal control of the Nexus but was ultimately defeated by her daughter. Exiled on Boreas by the Heart Of The Universe, she befriended the Winter King and became his trusted advisor.
Leiko is a human with no powers. Her mind has been altered by the Core, boosting her intelligence and giving her easier access to alien technology; it may also be responsible for her total lack of empathy.
- While arguably the weakest of all the Vanguard's enemies, she's the only adversary from the first 50 issues still around
- Leiko was selected as Time's Person Of The Year before her daughter, much to Noriko's annoyance
- She's been shown to speak both English and Russian fluently. She likely knows Olympian as well.
- Beyond The Impossible #2, "The Vanguard": meets Noriko
- Beyond The Impossible #46, "Flashback, Part 1": tells Noriko the truth about her origins
- Beyond The Impossible #68, "Empire of Shadows": leads the Empire of Shadows on its first attack
- Beyond The Impossible #88, "Nightmare": fights Abyss
- Beyond The Impossible #95, "Convergence": body taken over by Noriko Null
- Beyond The Impossible #108, "The Mist": becomes Minister of Defense of Japan
- Beyond The Impossible #162, "Unexpected arrival": orders the invasion of North Korea
- Beyond The Impossible #190, "Justice": exiled by the Heart Of The Universe
- Beyond The Impossible #205, "The Winter Castle": revealed to be working for the Winter King