Each monster resembles one of the Egyptian Gods and are seen as dark counterparts to them, in a similar vein to the Wicked Gods (though unlike the Wicked Gods, they are never stated in-series to have any relation to the Egyptian Gods). In gameplay, they also have similarities to the Egyptian Gods - they must be summoned by sacrificing 3 cards of a certain type, However, the Sacred Beasts are not limited to using monsters, and they are substantially easier to summon than the Egyptian Gods, which comes at the cost of being generally weaker.
The designs of the Sacred Beasts, "Uria", "Hamon" and "Raviel" were overseen by Kenichi Hara. Each of them resembles one of the three Egyptian Gods; "Uria" finds a counterpart in "Slifer the Sky Dragon", "Hamon"" in "The Winged Dragon of Ra", and "Raviel" in "Obelisk the Tormentor". Also, like the God Cards, all three Sacred Beast Cards have the same background. Unlike the God Cards, however, they possess certain visual cues that make them distinct from their predecessors, including translucent wings and more pronounced claws and skeletal features.
The three Sacred Beasts are named after characters in Judeo-Christianity. Uria's name is an alternate spelling of the name of Uriah, a man who was murdered by King David because David had an affair with Uriah's wife. Uria may also be a reference to the archangel, Uriel, whose name means "God's Flame", and who guards the flames of Purgatory. Hamon's name originates from the Book of Esther (Hamon is considered an alternate spelling of Haman, a villain who tried to depose the King of Persia and kill all the Jews in Persia. Also the word Hamon means blade pattern, referring to the wave like patterns found on Japan's iconic weapon). Finally, Raviel's name is an alternate spelling of the name of Raziel, the angel of mysteries. Armityle, the fusion of all three Sacred Beasts, is named after Amitiel, an angel of truth in Judeo-Christianity, who some consider to be an archangel.
In Yu-Gi-Oh! GX, the Sacred Beasts are legendary creatures whose cards were sealed by Kagemaru underneath Duel Academy behind the Spirit Gates, which requires seven Spirit Keys to open, as he could not unlock their power at the time. Should they ever be set free from their stronghold, chaos and darkness will envelop the world, destroying everything.
The Shadow Riders sought to acquire the Spirit Keys and revive the Sacred Beasts. In order to open the gate, a strong Dueling presence is required; if the keys are stolen and placed in the gate (as attempted by Don Zaloog), nothing will occur. To meet the challenge of the Shadow Riders, seven of Duel Academy's finest Duelists were selected: Jaden Yuki, Zane Truesdale, Chazz Princeton, Alexis Rhodes, Bastion Misawa, Lyman Banner (the only Shadow Rider to get his key by default, due to the fact his true identity was unknown at the time) and Vellian Crowler. Although the Shadow Riders were defeated, Kagemaru managed to awaken the Sacred Beasts because of the Dueling energy released from the Duels. In exchange for freeing them from imprisonment, the Sacred Beasts slowly returned Kagemaru to a youthful state, empowering him with the energy sapped from Duel Monster spirits, but Jaden's interference resulted in the man's downfall. They were thus locked away once more.
After Duel Academy is transported to an alternate dimension in the third season, a Yubel-possessed Marcel Bonaparte retrieves the Sacred Beasts and builds a Deck around them, which boosts the Summoning speed of the Sacred Beasts and also supports the Summoning of their combined form, "Chaos Phantasm Armityle". When Jesse Anderson reappears after he was possessed by Yubel, he uses them in a Deck based around quickly Summoning the Beasts and "Armityle" for his Duel against Adrian Gecko. Although Yubel didn't use them in her final Duel with Jaden, "Raviel" was shown to be in her Deck. After Yubel merged with Jaden, they are safely returned to their resting place.
The main drawback to this Deck is that it relies heavily on Traps, so "Jinzo" or "Royal Decree" will completely cripple it. However note that "Royal Decree", unlike "Jinzo", does not negate the activation of your Continuous Traps, so they will stay on the field, thus allowing you to still Summon "Uria". "Royal Decree" can be used alongside "Uria" as well.
This Deck type is a hybrid of the three previous decks and is focused on Summoning the three Sacred Beasts and their fusion, "Armityle the Chaos Phantom".
While this Deck can use cards that allow the three Sacred Beasts to function, it is very taxing on Deck space and consistency. A better alternative is to focus on two or even only one of the three Sacred Beasts and use the first effect of "Dark Summoning Beast" to summon the remaining ones at a time.