Maria Balthasar (マリア・バルタザール, Maria Barutazāru?) is the young daughter of Gear designer Nikolai Balthasar and the granddaughter of "Old Man" Isaac Balthasar. When Maria was a little girl, she was captured by Solaris along with her mother and father and held hostage as incentive for Nikolai to construct a next-generation series of Wel-Gear hybrids. When the first model Seibzehn was created, he secretly programmed it to escape from Solaris and take Maria with it back to Shevat. Ever since, Maria and Seibzehn had been standing guard in Shevat and defending the aerial nation from anyone who would try an attack or approach it.
In battle, Maria herself is not a very strong character, since she is incapable of performing Deathblows. Her only saving grace is the fact that she can remotely call in Seibzehn to perform some powerful special attacks. In a Gear however, she's much different. Seibzehn is a powerful gear in combat, with attacks and special abilities that rivals the Xenogears. Maria was meant to have an Omnigear known as El Seibzehn but the idea was scrapped before the game was released. However, a concept sketch of the Omnigear does exist in the Perfect Works, the companion piece to Xenogears.