The NightWing Fortress, made from tunnels of volcanic rock, had been the previous home of Queen Battlewinner, Princess Greatness (Royalty), and around 200 other NightWings living in the former Night Kingdom. Unlike the other palaces and fortresses, the NightWing Fortress couldn't be seen on the map of Pyrrhia. Starflight's father, Mastermind, was working on a way to protect the fortress from eruptions until the project to study RainWing venom started. It later exploded from the volcano eruption. Since then, the NightWings had lived in the Rainforest Kingdom. It was introduced in The Hidden Kingdom and is the main setting of The Dark Secret. It also is rumored that this fortress holds one of the three Dreamvisor's created by Darkstalker, Starflight found one of them in a abandoned treasure room on a destroyed part of the island. He and Fatespeaker were exploring before the volcano exploded, and they found two dead Nightwing guards. Then he found one of the three, and it was stolen from him two nights later by Flame.
While exploring the fortress, Starflight and Fatespeaker stumbled upon a collapsed section of the building, coated in lava. It was an old treasure room, sealed during the volcanic eruption that occured eleven years prior. Starflight came across it and found two deceased NightWings who were unable to escape. One of them was holding a dreamvisitor, which Starflight took.
When the volcano exploded a second time, the fortress was destroyed by lava, forcing the entire NightWing tribe out of their home. Luckily for them, Queen Glory was merciful enough to let them join the RainWings in the rainforest.
The fortress houses the queen of the NightWings and most of the tribe. Rooms included a huge library full of scrolls, Mastermind's lab where he conducted experiments (such as the prototype for Queen Battlewinner's armor and documenting information on the RainWings and their venom), the Council where Starflight was interrogated in front of his tribe, and dormitories for dragonets. It also included the Throne Room that housed Queen Battlewinner's private chambers, which were only accessible through a secret entrance hidden behind a map of Pyrrhia. She was able to pass orders to Princess Greatness through a screen called the Queen's Eye. The fortress also has dungeons and prisons, some of which were used to hold the captured RainWings.
Before the end of the The Dark Secret, the NightWing volcano island was accessible from two locations. The first was the animus tunnel created by Stonemover. It led directly from the Rainforest to the volcano island. The second was to fly to it over the sea. It could be found if a dragon flew north from the Claws of the Clouds Mountain in the Sky Kingdom. After the end of the fourth book, the animus tunnel was covered by lava from the exploding volcano.