Complex sentence: Catellite (ostensibly the wizard's cat) which is is also spherical in form normally follows the wizard, but it can also be moved independently by holding down the fire button whilst moving the joystick (which meanwhile renders the wizard uncontrollable).
Split into simpler sentences: Catellite (ostensibly the wizard's cat) is also spherical in form. It normally follows the wizard, but it can also be moved independently by holding down the fire button whilst moving the joystick (which also renders the wizard uncontrollable).