Essentially, the Ryloth Ark was a rectangular, oblong chest plated with gold. Covering the box was a golden lid adorned with two sculptures of winged Twi'leks, humanoid non-Humans with two "brain tails" emerging from the back of their head. The two Twi'leks faced one another, and their wings, which wrapped around their bodies, touched between them. On the bottom of the box, four gold rings were attached, through which two staves could be put, allowing a duo to carry the Ark.
At least two Arks existed, with one falling down a crevasse on Ryloth.
The treasure display on Scardia Station
As its name suggests, the Ryloth Ark originated on Ryloth, a rocky planet of the Outer Rim Territories inhabited by the Twi'leks. Throughout history, several replicas of that artifact were crafted, and the Ark became the focus of Piethet Brighteyes and the raiders of the Ryloth Ark, a popular work of fiction that gave dreams of adventures to young boys such as Treuten and Kosh Teradoc from Er'Kit. During the pan-galactic conflict known as the Clone Wars, the Ark fell prey to the cupidity of the Confederacy of Independent Systems—an affiliation of worlds that had seceded from the Galactic Republic and waged war against it. Around 22 BBY, the Skakoan Emir Wat Tambor invaded Ryloth in the name of the Confederacy. While the Republic's Grand Army launched an attack to liberate the planet, Tambor raided the vaults of the Twi'leks and had many priceless artifacts loaded on board his personal shuttle. The Ark was one of them, and it was taken away by TA-175, Tambor's tactical droid, even as he left his master behind. The Republic ultimately won the Clone Wars, and its Supreme Chancellor Palpatine declared a New Order, anointing himself Galactic Emperor.
In 5 ABY, twenty-seven years after the Battle of Ryloth, it appeared the Ark was in the possession of the Church of the Dark Side, a charade religion established by the Imperial Intelligence following the death of Palpatine. The so-called Prophets of the Dark Side kept it in a glass-walled display case on Scardia Station, along with a rare set of blood-red Mandalorian armor. However, it remained uncertain whether the Prophets owned the genuine article—retrieved from the long-defunct Separatists—or a mere copy. Regardless of its authenticity, the Ark owned by the Church of the Dark Side was lost when Grand Admiral Afsheen Makati destroyed Scardia Station.
R2-D2 and C-3PO near the Ark (as hieroglyphs) in Raiders of the Lost Ark
The Ryloth Ark first appeared in "Liberty on Ryloth," the twenty-first episode in season one of the Star Wars: The Clone Wars television series. It was inspired by the real-life religious artifact known as the Ark of the Covenant. According to the Jewish Tanakh and the Bible, the Ark of the Covenant was a wooden chest plated with gold in which the stone tablets inscribed with the Ten Commandments were housed.
A famed, long-lost artifact in real life, the Ark was the focus of the first Indiana Jones movie, titled Raiders of the Lost Ark. Since Star Wars creator George Lucas also produced the Indiana Jones franchise, the Ryloth Ark was added into The Clone Wars as an homage.
In the "Ask Lobot" feature of Star Wars Insider 111, the Keeper of the Holocron continuity database, Leland Chee, declared that the Ark of the Covenant's presence in "Liberty on Ryloth" was just "a fun Easter egg to look for" and not meant to be part of the Star Wars continuity. However, the artifact has been explicitly brought into the Legends continuity by authors Greg Mitchell and Abel G. Peña, who mentioned the Ryloth Ark and its numerous copies in The Star Wars Spy Game: SPIN Declassified, an article written for the official StarWars.com blog. In Part 2 of The Imperial Warlords: Despoilers of an Empire, another official blog article, Peña also mentioned a work of fiction called Piethet Brighteyes and the raiders of the Ryloth Ark.