TV-Series
Description
Hailing from Gundalia, Mason Brown serves as a Subterra brawler within the Gundalian Agents. Operating directly under Ren Krawler during their infiltration of Bakugan Interspace, Mason commands Subterra Avior equipped with Battle Gear Lashor. Though initially aligned with Emperor Barodius, his true loyalty rests with Gundalian elder Nurzak.

Mason exhibits arrogance and a penchant for showing off, frequently blaming Avior for non-battle setbacks. Their relationship is contentious; Mason derisively calls Avior "old timer" or "old dog," while Avior views him as a smart aleck. Despite this bravado, Mason accepts battle losses calmly and holds no grudges, exemplified by his reaction to defeat by Jake Vallory. He demonstrates respect for Neathian figures like Fabia Sheen, admiring her Bakugan's abilities and showing possible romantic interest—prompting Avior to tell him to "quit flirting."

His mission begins by testing the Battle Brawlers' strength, defeating an unnamed Ventus brawler and initially overpowering Jake Vallory, though losing a rematch after Jake receives coaching from Julie Makimoto. As part of Gundalian operations, Mason and Lena Isis deliberately lose to top-ranked players to lure them for hypnosis by Kazarina. He later partners with Sid Arkale to defeat brainwashed humans Taylor and Casey.

Following repeated failures, the Gundalian Agents face punishment from the Twelve Orders. Mason escapes this fate by fleeing Kazarina's reconnaissance mission with Nurzak, striking down guards to avoid capture. During their escape, an energy surge from the Sacred Orb transports Mason and Avior between dimensions. Resurfacing in Neathia, they join the Battle Brawlers to rescue Jake Vallory.

Mason aids in freeing former teammates Lena Isis, Jesse Glenn, and Zenet Surrow from Kazarina's brainwashing. He guides Fabia and Ren to Nurzak's hideout for strategic planning and participates in the final battle against Barodius. Though defeated alongside Jesse and Zenet by Phantom Dharak, Mason survives and returns to Gundalia post-war.

Later, he defends Gundalia against Chaos Bakugan alongside Avior, Jesse, and Plitheon during Mechtanium Surge conflicts. His recorded Bakugan include Subterra Avior, Lashor (Battle Gear), Koptorix (Mobile Assault), Fortatron (Battle Suit), Crashbor (Mechtogan), and Sceptor (his second guardian Bakugan in Mechtanium Surge).

Mason is the only Gundalian Agent besides Ren to evade punishment from the Twelve Orders. His human disguise appears less muscular than his true Gundalian form. He shares a surname with the unrelated human Joe Brown and shares narrative parallels with Shadow Prove regarding emotional outbursts during failures.