Watch Batman: Soul of the Dragon (2021) online

In his younger years, while training himself to become a vigilante crimefighter, Bruce Wayne travels to Nanda Parbat, a secret monastery in the Hindu Kush Himalayan region, where he meets its caretaker, O-Sensei, and five other students training in the martial arts: Shiva, Richard Dragon, Jade, Ben Turner, and Rip Jagger. O-Sensei eventually entrusts Shiva with Soul Breaker, a Muramasa sword in his possession, but otherwise remains secretive about a certain door at the monastery's outer perimeter. One night, Rip penetrates the forbidden door and kills Jade with Soul Breaker, which is the key to a mystical gate O-Sensei was guarding. This gate opens to the home dimension of the serpent god Nāga; four of his servants emerge and devour Rip before turning on O-Sensei and his students. Bruce and the others kill the demons, but to close the gate, O-Sensei sacrifices himself by entering Nāga's realm. The chamber then collapses, leaving only the gate intact.

Years later, Richard discovers that millionaire Jeffrey Burr, leader of a dangerous snake cult named Kobra, has gained possession of the gate. Richard travels to Gotham to ask Bruce for help, but they are attacked by a gang hired by Burr's chief killer Schlangenfaust. During this fight, Richard learns that Bruce is Batman and that Schlangenfaust is looking for Soul Breaker. They head for Gotham Chinatown to inform Shiva, the resident crimelord, but the cultists attack them there, and Schlangenfaust uses the distraction to steal the sword. Needing assistance, the three recruit Ben, and together they track the cult to a heavily fortified island where the cult has taken the gate and are preparing to open it by sacrificing several kidnapped children to Soul Breaker. They also learn from Ben that years ago he had tracked Kobra after discovering that Rip was one of their members, and that he learned that due to an obscure prophecy, Burr means to become Nāga's earthly avatar.