Isabel Magnolia is one of Levi's companions, the other being Farlan Church. She, Levi and Farlan get caught by the Survey Corps Squad Leaders Erwin Smith and Mike Zacharias. She was threatened by the Survey Corps in order to force Levi join Erwin's division. She's a very talented 3DMG user, but how she learned to use it and how did her group get the equipment is still unknown.
Isabel is an energetic character who's confident in her abilities. She handles the maneuver gear well and calmly. She also has a defiant streak, shown when she keeps struggling against the soldier who captured her. She also cares for her friends, sacrificing information to save Levi from getting hurt more.
With Levi joining the Survey Corps, she and Farlan too joined the Corps, only to be killed during the expedition.