The Rider (ライダー, Raidā?) Class Card of the Fifth Ainsworth Holy Grail War was granted to Kariya Matou in Fate/kaleid liner PRISMA☆ILLYA. It was later one of eight Class Cards transported to Illya's world.
Medusa's dress, arm-wear, and leggings have a tattered appearance, and they leave a number of small patterns on her skin. Breaker Gorgon is greatly changed, showing a pattern with an eye in the middle. She fights straightforwardly with her dagger, overpowering her opponent.
Fate/kaleid liner PRISMA☆ILLYA
When manifested, Rider's appearance is altered in a number of ways. Her dress, armwear, and leggings have a tattered appearance, and they leave a number of small patterns on her skin. Breaker Gorgon is greatly changed, showing a pattern with an eye in the middle. She fights straightforwardly with her dagger, overpowering her opponent. Rin and Illya are unable to do any lasting damage due to Illya's inexperience. Before Rider can use Bellerophon, Miyu arrives and uses Gae Bolg to slay her and obtain the Class Card.
Medusa's specialty is utilizing her high agility to perform acrobatic maneuvers that lead the opponent on and provide her the momentum in battle, but she is lacking in hand-to-hand combat ability. She can summon a Pegasus and Bellerophon, a golden bridle able to control any mount. She predominately utilizes it for the Pegasus, granting it a rank up in all parameters upon releasing its true name. Its magical energy is gathered, becoming a "shooting star" as its "super-charge" pulverizes the target.
Her Mystic Eyes that can petrify targets simply by sight are sealed by Breaker Gorgon, a Bounded Field meant to confine the consciousness of a target to watching a "nightmare of both delight and taboo" while sealing all abilities they possess in the outside world. It takes the form of a visor to seal her Mystic Eyes. Her Mystic Eyes are of the highest class, Jewel, and they can entrap, paralyze, and slowly petrify the opponent with a glare. Those that can resist will be exposed to a "pressure" effect that lowers all parameters by one rank.
Including the Rider Class Card grants the user Medusa's Iron Stake, stakes fastened to iron chains. They possess no overt abilities, but they are hard to remove from the opponent upon stabbing them.
Installing the Rider Class Card grants Medusa's outfit, combat abilities, and Mystic Eyes. They can summon the Pegasus, turning the Iron Stake into Bellerophon's bridle of light, allowing them to force the Pegasus to charge. Both of Miyu's eyes are converted, but only one of Illya's becomes a Mystic Eye.
Berserker Class Inheritance
Through Berserker Class Inheritance, Gorgon is manifested. The form bears an exact resemblence to the Avenger-Class Rider except how only one eye is covered instead of both.
As a result of the Inheritence, Rider gains a major increase in strength and speed through the Mad Enhancement and able to use a deadly poison from the hair which can manifest into a snake.