Bigieu, also known as Isabella, is an antagonist in the game Seiken Densetsu 3. She is a powerful, magic-wielding, cat-like demoness originating from the Underworld, Mavolia. She is the right-hand woman of the Dark Prince (one of the three possible final bosses of the game) and the archenemy of Hawkeye, one of the six playable characters available. If the player selects Hawkeye the ninja thief or Lise (Riesz) the amazon princess as the first playable character, the Dark Prince will be the game's primary antagonist and Bigieu will be the second-to-last boss. Her main goal is the revival of the Dark Prince and the restoration of his soul, as not only is she absolutely loyal to her Prince but she also has unrequited romantic feelings for him. She acts with Jagan to accomplish her goal.
- A very similar looking character that also goes by the name Isabella appears in Sword of Mana. They also share the ability to change into a cat like beast. It is unclear if the two characters are supposed to be one and the same person, or if it is more of a cameo.
- Fanha from Seiken Densetsu 2 is somewhat similar to Isabella of Sword of Mana and Bigieu of Seiken Densetsu 3.
- Despite all the terrible acts that Bigieu commits for the Dark Prince, she's hinted at having a kinder side. Apart from her desire to regain his soul, if the Dark Prince's remains are destroyed by the other villains, she kills Jagan and frees Elliot (who was meant to serve as the Dark Prince's vessel upon his revival) since she has no use for him.