Rex is a Ruasonid (a dinosaur like ghost) and the ghost who faced Danny durring the explosion at the Nasty Burger in the unaltered timeline (without the interference of Clockwork) . He is the king of the Ruasonid and one of the six main antagonists of Danny Phantom: Wraith alongside Dan Phantom, Caroline McLain, Sitic, Umbrus and H'rull.
Rex is vile, snarky, scheming, wise-cracking, intelligent and cool-headed, yet cold-blooded, bloodthirsty, merciless, and homicidal ghost. A animal with a great intellect and sharp sense of humor, Rex speaks in a somewhat brutish yet polite, gravely, unsettling playful and civilized tone of voice and was possessed of a bitingly sardonic wit. Rex's power is also matched by his sadism as he prefers to kill humans in cold blood or sadistically torture and inflict pain on his enemies instead of playfully scaring people unlike most ghosts, whether there're children or not.
He also has a strong manipulative streak that far exceeds Vlad's. He is also a brilliant strategist as he finds tries to find ways of getting past Clockwork's ability to see through time by using multiple alternatives in the event one of them might fail. His main goal is to eradicate all life on Earth the same way he did to the Dinosaurs a millennia ago. Despite this, Rex is a fair (yet mischievous) boss who treats his underlings with respect and is very lenient with them as he tends troll his minions instead of actually punishing them. He also genuinely loves his wife Caroline, his daughter Raptor and his son Blaze.
He is a 9'2" feet tall humanoid Tyrannosaurus like ghost with pitch black skin covered in snow white bones (except his biceps, triceps and legs) with glowing blue lava, has dark blue claws and toe nails, black sharp teeth, red eyes and a purple Tongue. His tyrant form (which first appears in the TV film season finale of the Ghost Zone Saga) is a foot taller and takes elements from a triceratops and stegosaurus, while maintain his tyrannosauridae like features. He then gains the King Tyrant transformation (which first appears in the season finale of the Ruasonid Saga), a much stronger form that's put's his power on par with the ghost king.
Rex is the one of the most powerful ghosts in the series, being able to have enough strength to take on the entire ghost zone and possibly destroy the Earth. His ghost powers are composed of volcanic elements and dark ecto-energy.
- Ghost Ray (Purple)
- Paranormal Strength, Speed, Agility, Dexterity and Durability
- Anti-Ghost Sense
- Pyrokinesis (Green)
- Magma Manipulation
- Due to the altering of the timeline, Clockwork managed to delay Rex's return.
- Unlike most ghosts in the series, Rex doesn't get along well with the others (except Caroline, his fellow Ruasonid and other infamous ghosts).
- He comes from a powerful race of dinosaur like ghosts called the Ruasonid (which is Dinosaur spelled backwards), who are often isolated from the rest of ghost zone as they were often at war and are feared throughout the realm.
- He is also one of the few Ghosts to call Danny by his real name, often referring to him as "Daniel" (similar to Vlad). He also does to Jack, often referring to him as "Jackie".
- His power almost rivals the power of Dark Danny (who is actually equally as strong as the ghost king).
- He also bears a similarity to the Hobgoblin from the Spider-Man comics as Rex replaces Vlad as Danny's primary enemy (a role also shared by his archenemy Dark Danny). He is however actually Jack Fenton's archenemy due to Rex causing a lot of harm to his family, such as brutally wounding his wife and sadistically killing his daughter.
- He replaces Vlad as Danny's chief enemy, due to causing numerous tragedies in his life, such as ruining Jazz's future, brutally wounded Maddy, defeating him in a humiliating way numerous time and worst of all destroyed Amity Park. He also killed Jazz at the end of season 3. He was also the ghost Danny faced in the unaltered timeline in which Danny's family and friends were killed at the explosion at the Nasty Burger during the Ultimate Enemy. This makes Rex the one indirectly responsible for the creation of Dan Phantom, making him one of the Phantom's most personal and significant enemies alongside his evil self.
- Due to the altering of the timeline Clockwork managed to delay Rex's return to the human to not only prevent Danny's terrible future, but to prepare him to fight Rex.
- He is also the third villain who tried to kill Danny's family and friends, the first being Dark Danny and the second being Freakshow.
- His personality is similar to the Beast Wars version of Megatron from the Transformers series.
- Due to the of lava in his veins, he is immune to Danny's ghost sense (a reference to Venom's ability to block out Spider-Man's spider sense).
- He is the most recurring and significant antagonist in series.
- He was inspired by Frieza and Cooler from the Dragon Ball Z series as well as the Tyrannosaurus Rex from the Jurassic Park franchise and other Dinosaur like villains. He also bears a resemblance to Monster X from Godzilla: Final Wars.
- He is also the lover of Ember Mclain's sister Caroline McLain.
- He also has ghost dinosaurs as both his pets as well as his minions. His personal favorites are his two T-Rexs Tyrannos and Razortooth.
- He is also one of the most feared ghosts in the ghost zone, due to his ruthlessness, power and merciless nature.
- He is only character to be the main villain in more than saga (namely the Amity Park, Rex, Ghost Zone and Ruasonid sagas).
- He is also the one who killed the dinosaurs.
- He has a rare and much stronger type of pyrokinesis known as Magma Manipulation as his powers are volcanic based.
- Unlike Vlad (who was a degrading evil in the original series), Rex is a more active and serious threat and doesn't make a fool out of himself (the same way Vlad did in later episodes in the old series).
- Despite being the series' primary antagonist, he only appear in seasons 2, 3, 4 and 9. He does however make a brief cameo in Season 1 as a silhouette.