Millions of years ago, an ancient Indian civilization went under sea and its people turned into sea humans to live in a golden aqua city they called Swarn Nagari. The residents of Swarn Nagari are far advanced in science and are completely non-violent. Dhruva helped them, when Grand Master Robo tried to invade and capture Swarn Nagari for all the gold, after accidentally discovering it. What actually happened was that Robo was conducting a nuclear missile test under-water, which went wrong. Though he could not achieve his immediate goal, he found Swarn Nagri meaning Golden City, which became his target now.
Dhananjay came to Rajnagar looking for a monster who had escaped from Swarn Nagari, and ran into Dhruv. During their fighting, he captured Dhruva in his 'swarn-pash' (golden trap), but he received a message to come back to Swarn Nagari immediately, so he tried to leave, but Dhruva though being incapable of breaking out of the swarn-pash, somehow managed to capture Dhananjay in the swarn-pash at the other end, and so Dhananjay had to carry him to the Swarn Nagri through his 'aayami dwaar' (inter-dimensional door).
Once there, Dhruva realised that the city is under siege by Grand Master Robo's troops, and he offered to help them.
Dhruva helped the Swarn Nagari people defend their city. Since then they became friends forever. And as a gift for his friendship and help, the scientifically much advanced Swarn Nagari people fitted a tiny instrument in Dhruva's body, which enables him to breathe and talk under water.