|“||Whoa, boss! I don't want to be a horse-ke-bob!||”|
Blackjack is Percy Jackson's friendly, pure black pegasus. He often serves as Percy's main option of transportation. Blackjack and other Pegasi often go to Percy, who helps them with their, or other creatures' problems.
|“||Gotcha, boss. Man, I hate seeing that boat!||”|
–Blackjack in The Last Olympian
Blackjack, originally introduced as a mare, manages to escape from Kronos' army ship where Luke had been keeping him prisoner. After Percy saves him from what Blackjack claims to be certain death, he devotes his eternal assistance to Percy. Blackjack resides in the pegasi stables in Camp Half-Blood.
At camp, before Percy goes off on his quest, Blackjack woke Percy up, telling him that there is a little sea friend that needs his help. Later on, he gives Percy a ride from Camp Half-Blood all the way to the Smithsonian Air and Space Museum in Washington, D.C. trying to catch up with Thalia Grace, Grover Underwood, Bianca di Angelo, and Zoë Nightshade. Blackjack wants to stop for donuts, and Percy tries to explain that a flying horse would give every cop in the place a heart attack. Blackjack leaves Percy to go back to Camp Half-Blood after a close call with Mr.D and flies back due to his exhaustion of constantly flying for such a long distance, though he does not want to admit it.
Later, Blackjack and his friends Guido and Porkpie appear to carry Percy, Annabeth Chase, and Thalia from a plane field near Mount Tamalpais to Olympus in order to attend the winter solstice meeting. Leaving them on a cheerful note, he asks Percy if he could use Percy's cabin as his stable if Percy does not come back alive. At Percy's incredulous expression, he quickly answers that it was "just a thought," before apologizing.
Blackjack speaks to Percy about the Labyrinth. He warns Percy about the dangers of the underground maze. Due to Percy's call, Blackjack, along with other pegasi, comes and carries Percy and his friends back to Camp Half-Blood after escaping the Labyrinth, but the Pegasus does not go with Percy.
Blackjack lands on Paul Blofis' car while Percy was out with Rachel Elizabeth Dare. He had Charles Beckendorf with him. Beckendorf and Percy, after an awkward farewell to Rachel, were carried by Blackjack to the Princess Andromeda, where he leaves on Percy's command.
During the Battle of Manhattan, he carries Percy and Annabeth as reinforcements to the Apollo cabin who were defending the Williamsburg Bridge against Kronos' army. When Annabeth suffers a serious injury, Blackjack manages to carry her back to the camp's headquarters at the Plaza Hotel opposite Central Park. When the Clazmonian Sow appeared, Blackjack and Percy pursued it, and with the help of some lion automatons made by Daedalus, they managed to defeat it. Finally, Blackjack was forced by Rachel to bring her to Camp Half-Blood so she could become the Oracle, much to the irritation of Percy.
Annabeth mentions that Blackjack is being used to search for Percy.
On a plane to Anchorage, Alaska, Percy remembers when he'd flown before. Though the details were a bit hazy, Percy remembers Blackjack specifically as well as the other times he'd been on a plane.
When Percy, Piper McLean, and Jason Grace are standing on a deserted highway trying to get to a mile marker called Topeka 32, Jason claims that he has a friend that could help them out. Percy claims the same thing and they both call their horses at the same time. Blackjack soon flies from out of the sky and Piper said that she had never seen a pegasus like that one before. When he lands, he asked Percy if he could have any donuts, to which Percy says they can later. When Jason's horse Tempest arrives moments later, it makes Blackjack a little nervous, but Percy calms him down.
Percy and Blackjack fly to the sign and meet Bacchus, who tells them he is there to meet Ceres. After Bacchus leaves because he senses a trap, Percy rides down the street on Blackjack and turns to face Jason, both of which had been possessed by Eidolons, on the orders of Gaea and they start fighting. While Percy managed to knock Jason off of Tempest, Percy was knocked off Blackjack with a bolt of lightning and Blackjack fell into the field below. As Percy and Jason fought some more until Jason was knocked out and Percy went in for the kill. Piper managed to slow him down with charmspeak, but not completely stop him. She held his attention until Blackjack walked up quietly behind Percy. Piper used her charmspeak to tell Blackjack to knock him out, resulting in Blackjack hitting Percy in the back of his head with his hoof. He then carried the unconscious boys back to the ship and spent some time on the deck with Gleeson Hedge before flying off.
Blackjack was one of the pegasi recruited by Pegasus to aid Nico, Reyna, and Gleeson Hedge in transporting the Athena Parthenos to Camp Half-Blood. Nico rode him to a ship docked off the shore at Long Island Sound where they settled to rest and plan their next move. Blackjack watched the ensuing confrontation between the demigods and Octavian's right-hand man, Michael Kahale and legionnaires loyal to Reyna, Dakota and Leila until they were rescued by Tyson and Ella. As the party separated, Reyna remained on the ship and collected her thoughts, regarding her family history until she was comforted by Blackjack, who reminded her of recently deceased pegasus, Scipio. However, the tender moment was interrupted when Orion shot an arrow into his flank. The pegasus, alive, but weakened, struggled to maintain his breathing as Reyna, armed with the power of Bellona and Athena defeated the giant. After she returned the ship, Reyna immediately treated Blackjack's wounds, saving the horse's life. He stayed behind to heal as the rest of the pegasi and Reyna delivered the statue to the Greeks. After the battle with Gaea, Nico mentioned that Blackjack was recovering from his arrow wound.
Blackjack has a highly informal personality. Although he is willing to serve Percy, he calls Percy "boss" rather than "Lord," as well as once calling Dionysus "the wine dude", much to the latter's annoyance. Blackjack has two best friends, Guido and Porkpie, who are also pegasi. Blackjack is extremely loyal to Percy, and shows a personality as being able to be loyal to anyone who proves their worth. He is seen as a friend for Percy when Annabeth is lost in The Titan's Curse, and is said to, "probably run himself into the ground before saying he's tired" when he's carrying Percy. Despite his initial dislike of Nico (due to him "smelling like dead people"), Blackjack eventually warms up to the son of Hades and has no qualms about having Nico ride him in The Blood of Olympus. Blackjack is also quite compassionate, comforting Reyna when things seemed hopeless to her.
- Percy mentions that he does not let anyone ride Blackjack except himself. However, Rachel did not care what Percy thought and she thought her needs were more important; Beckendorf had permission from Percy. Nico later rides him when Pegasus recruits Blackjack to help carry Athena Parthenos. Its stated that while he usually carries Percy, he doesn't mind carrying others if need be.
- Ever since Percy indirectly freed him, he thought of Percy as a hero. So much so, that he woke Percy up to help any creatures that he could not help himself (like the Ophiotaurus caught in a fishing net).
- Blackjack only addresses Percy as "Boss," much to the latter's annoyance.
- In The Last Olympian, Percy figures that Blackjack would rather have his mane braided like "My Little Pony" rather than go back to the Princess Andromeda.
- His gender is somewhat inconsistent as in The Sea of Monsters he is referred to as a mare and a "she," but from The Titan's Curse onward, Percy refers to him as a male. The problem was asked by a fan at a Rick Riordan book talk. He replied "Either Percy's mixed up, or it's a mistake by the author, which, of course, could never happen".
- Bellerophon, in ancient Greek mythology is also known to have been given a pegasus by the goddess Athena. Whether this creature was black or not is unknown but he has been portrayed as such in several cases.
- In The Kane Chronicles: The Throne of Fire, Carter thinks he sees a flying horse. It could possibly be Blackjack during The Titan's Curse or The Last Olympian.
- When asked if Rick Riordan would rather have Blackjack or Festus, he replied: "At the risk of hurting Blackjack's feelings, Festus for sure".
- In the film, Clash of the Titans, the main hero Perseus has a black pegasus, very similar to that of Percy having the real name of Perseus and having Blackjack.
- Coincidentally, Blackjack appeared in every third book cover, The Titan's Curse and The Mark of Athena.
- Blackjack is blue on the cover of The Mark of Athena.
- On the Spanish Percy Jackson: Sea of Monsters film poster, at the bottom shows a Black Pegasus that is claimed by many fans to be Blackjack.
- Due to the fact that Blackjack is a descendant of the original Pegasus, a son of Poseidon, he and Percy are indirectly related.
- Blackjack was referred to as a mare on the Princess Andromeda when Luke calls for his steed.