The Nebula Armlet is a secret item found in Phoenotopia and possibly Phoenotopia Awakening. It allows Gale to focus her Ki more efficiently, thereby allowing her to charge up her attacks much more quickly than before.
The Nebula Armlet is located in the caves of Atai, which can be accessed by jumping into the water well in the middle of the city or through one of the passages in the Bandits' Lair. From there, the player needs the Floaty Donut to swim across the water and enter the caves. The Armlet is found in an ancient facility within the caves.
This facility can approached from two sides, one using the Atai water well entrance and the other from the Bandits' Lair. The Bombs are required to clear out rocks that block the entrance. From the water well entrance, the Javelin or Rocket Boots are required to climb a ledge that can't be jumped over. From the Bandits' Lair side, the Artifact is also needed as the caves in that direction contain Ancient Sentry Towers.
The facility contains several rooms full of Zombots that must be disposed of before advancing. This includes Red Zombots that can't be destroyed by Gale and must be lured and dropped into fire pits. Once all the Zombots in a room have been destroyed, the next room becomes unlocked until the final room where the Nebula Armlet can be found in a chest.