Fright Knight

Fright Knight is an ancient and powerful ghost, self-described as the spirit of Halloween and both The Ghost King's minion and second-in-command.

Apperance
In the episode "Fright Night," Fright Knight, described as 'The Spirit of Halloween,' was released as a result of Danny attempting to borrow his sword for a haunted-house decorating Halloween contest. He chases after him and takes over Amity Park with his sword, the Soul Shredder, which causes people to disappear to a dimension where they experience their greatest fears (which include Mr. Lancer in a dimension where he is forced to constantly scratch a chalkboard while doing calculus equations, and Tucker on a deserted island in his boxers with no technology). His sword is also one of the few things that dwell in the Ghost Zone that has a corporeal form, as Danny was able to grasp it in his human state, though it seems to lose this quality upon entering the real world. Fright Knight also rides around on a bat-winged Pegasus ghost known as Nightmare. Danny, however, managed to trap him inside a pumpkin by placing his sword inside and saying the poem to seal him within it.

Reign Storm
He returned in Reign Storm where it is revealed that he was a servant of Pariah Dark. He helps his master take over Amity Park, but at the end, turns into one of the many ghosts who turns against the king. He also apparently made a deal with Vlad Plasmius, though it is unknown what that deal is. It is most likely that he works for Vlad now. In the end, he appears right behind Vlad to help Danny trap the king so that he wouldn't harm/kill/maim anyone. Until the next time someone opens the Sarcophagus of Forever Sleep.

The Ultimate Enemy
In the beginning of "The Ultimate Enemy," he works for Dark Danny in an alternate future. He attacks Valerie after the Ghost Shield goes down and basically chases her into Fenton Works.

Frightmare
He made a cameo in "Frightmare" in a dream sequence of Danny's while he was under a sleep spell from Nocturne.

Phantom Planet
Fright Knight's final appearance is in the series finale, "Phantom Planet." He is one of the many ghosts who helps Danny and Skulker turn the entire planet intangible, so that an asteroid can pass through it.

Powers
Fright Knight is a powerful and strong ghost, powerful enough to overpower Vlad quickly. These are the powers he has displayed, though it's unknown if he has anymore:
 * Flight and hovering: Standard ghost powers, sometimes aided by his horse, Nightmare.
 * Intangibility and invisibility: Standard ghost powers.
 * Ghost Ray: He is able to fire pink ghost rays from his eyes. Often used as a primary ability, such as shooting down Danny for taking his famed Soul Shredder.
 * Flaming Crystal Meteor: Able to fire purple flaming crystal meteors with an incredible destructive power.
 * Superhuman Strength: Able to lift someone off the ground with little effort and throwing them through walls with nothing more than a mere move with his hand, as well as open the doors to the Fenton Portal and break the walls, very easily. He is also able to knock a person or ghost unconscious with one punch and hold ghosts as strong as Vlad Plasmius in a unbreakable grip with one hand. In short, those muscles are not just for show.
 * Superhuman Durability: Fright Knight is considerably durable, as shown during both his main appearances. Physical attacks have little if any effect on him. Only the greatest physical force, energy beams and explosions can damage him, but only stop him for a short while, before he returns to the fight, showing no wounds whatsoever. In Fright Night, Danny threw him at a giant clock that only disoriented him briefly. In Reign Storm he survived the combined attacks of Valerie, Danny and Vlad without any wound or injury, the only result was leaving him stunned for a few moments.
 * Superhuman Stamina: He can fight for nearly hours on end without having any signs of fatigue.
 * Teleportation: He can do so with both his sword's power and his own, disappearing in an explosion of bats (Only with his own power does it take that form).
 * Telekinesis: In the episode Reign Storm, he was able to summon his sword from a long distance