The Eye of Onyx is an animus-touched object that is part of the SandWing Treasure, described as being a black cabochon accented with dragon wings made from molded, beaten gold. The wings are red-gold-orange in color on either side (thought by Sunny to resemble the "Wings of Fire" from The Dragonet Prophecy), and set on a chain of hammered golden links. The sphere is most likely made of onyx, (hence its name, the "Eye of Onyx"). It was created by Jerboa to choose the best possible dragon to be queen.
Whoever holds the Eye of Onyx rules the Kingdom of Sand, provided that the last SandWing queen is dead. Therefore, if Princess Blaze, Princess Blister, or Princess Burn were to have the Eye, they would have become queen, stopping the war, as Sunny did in The Brightest Night. Sunny had given it to her mother, Thorn, the leader of the Scorpion Den and the Outclaws. Afterward, Blister attempted to steal it, resulting in her death, as the Eye deemed her unworthy. Since the current queen hadn't either died, or given Blister the Eye of Onyx willingly, she was electrocuted and reduced to nothing but a pile of black dust. Thorn is the current owner of the Eye of Onyx.
In Darkness of Dragons, Vulture and Onyx attempt to steal the Eye, trying to make Onyx the queen, but they ended up taking a replica that Thorn kept in her treasury instead, inadvertently saving their lives. During the sandstorm caused by Qibli using Princess Anemone's animus-touched copper bands to control the weather to save Thorn from "dying", Thorn mentions that the Eye of Onyx actually had a history of choosing commoners over royalty. This is because of the cleverly written spell cast upon it by the ancient SandWing animus, Jerboa. Thorn theorizes that the SandWing queen back in Darkstalker's time was most likely trying to get Jerboa to create something to keep herself in power. However, Jerboa tricked the Queen and instead wrote a spell that made the Eye of Onyx pick good queens or the best queen available for the job. This is why when the Eye of Onyx was handed to Thorn, it did not reduce her to a pile of dust.
- A dragon who is unworthy of being queen of the SandWings will be electrocuted and exploded into a pile of dust (like Blister), while one who is worthy may hold and wear it safely.
- The Eye was thought by Sunny to be what the false prophecy meant by "If she bows to a fate that is stronger and higher, she'll have the power of Wings of Fire", given the golden wings on either side of it.
- An onyx is a type of black gemstone, although it can rarely have other pigments.
- Onyx was named after it, as a hint to her royalty. This was confirmed in Darkness of Dragons.
- The jewel was enchanted by Jerboa (not daughter). Queen Thorn's theory was that Jerboa was playing a trick on her queen (most likely Queen Scorpion) who wanted something to keep her in power instead of the Eye of Onyx's actual enchantment.
- Sunny was technically queen of the SandWings for the few moments while she was holding the Eye of Onyx because the Eye did not turn her into a pile of dust.