Halo Dragon is an ancient and powerful Bakugan.
Back in the early ages, when Zindiga and Xia were young planets, the evil Bakugan Sphinxus rose to power. He seemed unstoppable, until this legendary beast appeared, and locked Sphinxus's powers away. After that, he flew into Zindiga's core, and went into a hibernation state.
It will appear later in Xian Infiltration.