He is a skeletal, split-nosed (with a seeming cleft lip and palate), wyvern kind of Bakugan who was an outcast due to the fact that he and his twin-sister, Wavern were not aligned with any of the six regions of Vestroia; they were known as The White Ones. He has no attribute, but pop-up effects are similar to Darkus Bakugan. He corrupted Alice Gehabich and Dr. Michael to become Masquerade and Hal-G respectively, and leads them in his quest to take both the Silent Core and the Infinity Core, and gain the power to take over the entire universe.
He's the most power-hungry Bakugan (to be nearly matched by Dharak/Razenoid in the third and fourth seasons). Also, he is the only main villain to be a Bakugan without a brawler, even though Hal-G is technically his brawler (however it can be said in reverse to many cases of evil partnerships/relationships where it is the Bakugan not the brawler who is dominant). Naga has also a deep hatred for the Battle Brawlers, specially for Dan and Drago (he is the reason for Dan and Drago met each other in the first place).
Naga and Wavern were born during the Great Revolution (the conflict turned into distortion, created by the only original Bakugan, Dharaknoid and Dragonoid), as they became trapped in the empty space between dimensions. When Drago was able to get across from his Pyrus Space, he could meet them both, but Naga only cared about himself and was angry for being born powerless. After Dr. Michael went to Vestroia by accident, they met each other for the first time. Michael explained to him about the Dimensional Transporter, unaware about his true motives. At last, Naga expelled Michael back to Earth and used a Dimensional Transporter Card he got from him to go to Vestroia's center, where the Cores were located.
After transporting himself to the center, Naga attempted to capture the powers of the Silent Core and Infinity Core, sources of negative and positive energy respectively of Vestroia, by going to them directly and absorbing them to fulfill what he believed to be his destiny. He failed, however, and was unable to control the power of the Silent Core, only being able to absorb the Silent Core after it trapped him inside; after that, catastrophic energy surge was caused due to the huge amount of negative energy was released and the Infinity Core became bonded to his twin-sister, Wavern, who was sucked into a portal to the human world.
This disaster caused the negative energy to spill all over Vestroia and the Earth, including the Bakugan on Earth as well as creating Hal-G (from Alice's grandfather, Dr. Michael) and Masquerade (from Alice) from two unfortunate people, who were exposed to excessive negative energy when Naga absorbed the Silent Core. He used them both to hunt for the Infinity Core from Wavern and also supplied them powerful abilities like Doom Cards (for Masquerade only) and thus, encountering the Bakugan Battle Brawlers, team of heroes, who were after the Infinity Core as well, to protect it from Naga. Naga created the Doom Cards for Masquerade, to send all fallen Bakugan to the Doom Dimension. At the first season finale, he was sent to the Doom Dimension (according to website Bakugan.com) while Drago became the Perfect Dragonoid and transformed himself into the new core for New Vestroia. In Season 2, many characters mentioned Naga (or what he did) even though he is not seen.
As Silent Naga
Silent Naga was a powerful Bakugan and could use Silent Core abilities. He became much larger and had purple veins around his body. When Naga fully absorbed the Silent Core, he became the second strongest Bakugan at that time (the strongest is Infinity Dragonoid). His wings were no longer attached to his hands. They resembled a cape and he had a sphere on his chest, in which the Silent Core is located and veins come out of there. He has two big horns on his head and red eyes.
In Ground Control To Major Dan, he attacked Earth to find Wavern with his troops. After seeing his Dual-hybrid Gatekeepers were defeated one by one, he decided to face Wavern himself, in The Good, The Bad and the Bakugan.
In The Final Brawl, Naga fought with Wavern until Drago destroyed her, on her request and sent her back to Vestroia as Naga said. Ultimate Dragonoid then took the Infinity Core and became Infinity Dragonoid.In Game Over, he lost because of Drago's Dextra Attack and was destroyed (or sent to the Doom Dimension as Bakugan.com said). It could be said that Naga's body was destroyed and his spirit was imprisoned within the Doom Dimension. Later, Drago took the Silent Core and reconnected it with the Infinity Core to become the Perfect Core of New Vestroia itself.