Slifer the Sky Dragon, known as Osiris the Sky Dragon (オシリスの
When Atem spotted Bakura, King of Thieves fleeing from the palace after he had attacked Aknadin, he chased after him on horseback and Summoned Slifer to fight Bakura's Diabound. Atem allowed Slifer to be struck in order to protect innocent civilians from Diabound's attacks and then got Slifer to force the battle into the sky. However Diabound was able to disappear into the darkness and attack Slifer from behind. Atem pretended to surrender his Millennium Pendant in order to distract Thief Bakura while he had Slifer sneak up on him. However Bakura got Diabound to make a similar sneak attack on the Pharaoh. After the priests arrived, Atem sacrificed Slifer, so that Seto's Duos could attack Diabound, but Duos wound up hitting a decoy ka instead. By defeating Slifer, Diabound gained its power, including its "Thunder Force" attack.
3000 years later, Maximillion J. Pegasus created cards depicting the three Egyptian Gods, for his game Duel Monsters. However the souls of the Gods came to dwell in the cards, making them powerful weapons. On realizing this, Pegasus regarded their creation as one of his greatest mistakes. He tried to destroy the God Cards, but could not bring himself to do it, so he had the Egyptian supreme council of antiquities bury the cards in different locations in the Valley of the Kings. The Rare Hunters managed to steal the "Slifer the Sky Dragon" and "The Sun Dragon Ra" cards. However the Egyptian supreme council of antiquities was able to prevent them finding "The God of the Obelisk". Ishizu Ishtar, from the council, later gave it to Seto Kaiba, so that he would host the Battle City tournament to retrieve the other two.
The leader of the Rare Hunters, Marik Ishtar, entered the Battle City tournament with the "Slifer" and "Ra" God cards. Using Doll as his puppet, he Dueled Dark Yugi in the preliminaries and used "Slifer the Sky Dragon" in the Duel. However Dark Yugi won the Duel and received the "Slifer" card through the tournament rules.
Dark Yugi used "Slifer the Sky Dragon" in his semi final Duel against Dark Bakura. Summoning it and attacking Dark Bakura became Dark Yugi's only way of winning the Duel. Marik exploited this, by having Dark Bakura remove his control over Ryo Bakura's body. Ryo, who was injured and significantly weaker than Dark Bakura would not be able to withstand an attack from Slifer, making Dark Yugi reluctant to attack. However, Dark Bakura took back control of Ryo's body and urged him to attack, assuring him Ryo would be okay.
During Dark Yugi and Kaiba's semi final Duel, when their cards "Slifer the Sky Dragon" and "The God of the Obelisk" destroyed each other, they were shown a vision of a past battle between Pharaoh Atem and Priest Seto.
Dark Yugi also used "Slifer" in his final Duel against Dark Marik, though it was swiftly destroyed by "Egyptian God Phoenix". Dark Yugi later revived "Slifer" to shield his "Obelisk" from one of the attacks from "Egyptian God Phoenix".
When Yako Tenma Dueled Dark Yugi for the first time, Yugi Summoned "Slifer" by sacrificing his "Magna Warriors", though Yako remained calm and proceeded to Summon his own "God card", "The Wicked Avatar", which was initially in the shape of a black orb before taking on "Slifer's" form. Yugi attempted to use "Slifer's" second mouth to destroy "Avatar", but the effect failed as "Avatar" was higher on the Divine Hierachy. "Avatar" then destroyed "Slifer" with a single attack, later revealed to be due to the "Avatar's" capability to take on the highest ATK on the field plus one.
Although consistently mentioned alongside the other Egyptian Gods, "Slifer" only made one more appearance, being used to offhandedly defeat Cedar Mill as Dark Yugi and Gekko Tenma raced to the top of the Kaiba Corporation building.
After relearning his true name from his friends, Atem blocked an attack from Zorc Necrophades and then Summoned the three Gods from the cards in Yugi Mutou's Deck. He then combined them into The Creator God of Light, Horakhty, who defeated Zorc.
Yugi and Atem constructed separate Decks for the Ceremonial Battle, which Atem needed to lose in order to pass on to the afterlife. Despite needing to lose, Atem gave the Duel his all. He included "Slifer" in his Deck, and discarded it at the beginning of the Duel as the cost to Special Summon "The Tricky". He revived it at the climax of the Duel, preparing to counterattack Yugi's "Silent Magician", but Yugi prevented the activation of "Monster Reborn" with "Gold Sarcophagus", sending "Slifer" back to the Graveyard and allowing him to win the Duel.
- ↑ 1.0 1.1 Yu-Gi-Oh! Millennium World Duel 21: "Assault on the Palace"
- ↑ 2.0 2.1 Yu-Gi-Oh! Millennium World Duel 22: "Slifer vs. Diabound"
- ↑ 3.0 3.1 Yu-Gi-Oh! Millennium World Duel 23: "Divine Light, Divine Shadow"
- ↑ 4.0 4.1 Yu-Gi-Oh! Millennium World Duel 24: "Surprise Attack! Power Attack!"
- ↑ 5.0 5.1 Yu-Gi-Oh! Millennium World Duel 25: "To Pierce the Darkness!"
- ↑ Yu-Gi-Oh! Millennium World Duel 35: "The Village of Ghosts!!"
- ↑ Yu-Gi-Oh! Duelist Duel 88: "The Lost Cards"
- ↑ Yu-Gi-Oh! episode 219: "In the Name of the Pharaoh"