The Obsidian Mirror is an animus-touched, oval-shaped piece of glittering black obsidian. Greatness was supposed to use it to spy on the RainWings, but did not, due to the fact that she did not trust any items created by animus dragons. It is said to not have performed as well since Stonemover may have done something to it. In The Brightest Night, Sunny described it as a kind of horrible, it made a sick, slithering sensation through her blood, as if it were pulling something out of Sunny's heart. She said it has a chilling wrongness to it, like the tunnels, that made Sunny's scales feel as if invisible spiders were crawling all over her. There is a theory it was enchanted by Darkstalker, as in Moon Rising he says "Enchant this mirror to spy on whichever dragon I choose".
It can be activated by saying the name of the dragon that you want to see, then by breathing smoke onto it. The dragons appear as colored tendrils of smoke, making vision unclear, but voices and background noises can be heard perfectly clear. In order to end the connection one must breathe fire over the surface of it, so this makes it impossible for IceWings, RainWings, or SeaWings to use the mirror, as they cannot breathe smoke or fire.
Preyhunter salvaged it from the NightWing's island before the eruption. The mirror was first used by Preyhunter to check if Glory and her friends care about Sunny, whom they had kidnapped. He states that it didn't work as well as it used to, and that Stonemover may have done something to it before he disappeared.
After she escaped, Sunny stole the mirror and used it to follow her captors to the the desert. To keep it safe, she buried it in the sand before entering the Scorpion Den, following the Nightwings. In the epilogue, Sunny tried to retrieve the mirror but she couldn't find it. Whether it had been stolen or swallowed by the sands is unknown.
Darkstalker might have revealed that he enchanted it or a device similar to it when talking to Moon.
Cobra, Qibli, and Winter visit Vulture's treasure, and then asks about the Obsidian Mirror. Winter answers, saying the NightWings used it to eavesdrop on any conversation anywhere in Pyrrhia. Then, Cobra suggests they steal it from her father's treasury, and reveals Vulture found the Mirror a few months prior, which is why he knew a lot about Winter and Thorn. Later, Cobra returns with a sack over her shoulder, and some fights later, Cobra enters Vulture's treasury, ordering Qibli, Winter, and Ostrich to fly to the palace, saying she will meet them there. After some conversation with Thorn, Smolder, and Typhoon, Qibli asks Thorn to arrest Cobra. It is revealed Cobra had been spying on Queen Thorn using the Obsidian Mirror, along with Vulture. Qibli orders four Outclaws to open Cobra's sack, revealing the Obsidian Mirror, chakrams,
knives, a black hood, a small glass vial that contained emerald-green liquid. Then, a guard pulled out a dragonflame cactus.
Qibli tells Thorn that Vulture has had the Mirror for a couple of months, and Thorn is horrified. Qibli then suggests they check on Queen Glacier, since she was in danger from the plague. Thorn activates the Mirror, and three IceWings are having a conversation, probably looking over their queen. One of them whispers Glacier was getting worse, and another says she has been sleeping since midday. The third IceWing says Narwhal is too sick to take charge and coughs. Winter then seems horrified about what he just heard, and then the first IceWing says "everyone is too sick to take charge." The second IceWing suggests asking for help, and wonders aloud if an IceWing is well enough to go to the Kingdom of Sand. Thorn is once again horrified and Winter is shocked about this.
Later, Qibli uses it to check on Moon, who is talking to Kinkajou about Darkstalker being evil. Next, he checks on Turtle who is imprisoned, and since he's not talking, he's either sleeping or sad. Next he checks on Darkstalker, who seems to be going around the kingdom checking on and talking to his citizens. Lastly, he checks on Tsunami, who they find out is captured (by Foeslayer but they don't find that out until later). When they head off, Qibli leaves the mirror with Thorn.