Jarasandha eyed Kamsa, the ferocious Yadava who was practicing along with the other Yadavas. Jarasandha was the king of Magadha and Magadha was an extremely powerful kingdom in the entire country.
Jarasandha was always on the lookout for new talents so that he could safeguard his already powerful kingdom and that was when he saw Kamsa. Jarasandha had no doubt about Kamsa's fighting ability. There had been a time when Jarasandha had tried invading Mathura. At that time, Kamsa alone was single handedly responsible for routing Jarasandha's army.
It was at that minute that Jarasandha decided that Kamsa was special and that he had to keep an eye out on the man.
Jarasandha saw Chanur, a trusted advisor of Kamsa talking with him and decided to take matters into his own hands.
Banasura was a powerful asura with a thousand arms. He was so strong and fierce that even the Devas themselves feared him. As if that was not enough, Banasura was an ardent devotee of Lord Shiva.
It is said that Banasura was such a powerful devotee that Lord Shiva himself had promised to be Banasura's protector.
This Banasura was the very one who eyed the powerful Kamsa in the kingdom of Mathura.
Realizing that Kamsa's brute potential would be wasted here, Banasura called the Yadava for private talks.
"You are extraordinarily powerful, Prince Kamsa." Banasura told Kamsa immediately as soon as Kamsa came to meet him.
Kamsa said nothing as he was studying the powerful thousand armed asura before him as Banasura continued, "You are not meant to be a mere prince. I can seen greatness in you. You are destined to be a king. The king of all the Yadavas everywhere, not just at Mathura." Banasura said in a quiet voice.
It was at that minute that Chanur came and wanted to talk with Kamsa.
Looking at Chanur and then at Banasura, Kamsa ordered Chanur to spill the news there.
"King Jarasandha of the Magadha kingdom wishes to form alliance with you, my Lord." Chanur told Kamsa with glowing eyes.
Kamsa was speechless. He really was.
Magadha was a powerful kingdom and it was a certainty that any person associated with that kingdom would have untold power.
"King Jarasandha has two daughters – Asti and Prapti. They are both willing to marry you, my Lord." Chanur finished with a quiet smile.
Kamsa was reeling under the news. He just could not believe that he would receive back to back news of this sort. An asura wanted Kamsa to take over Mathura and at the same time a powerful king wanted to offer his daughters in marriage to him....
The words of both the people worked its magic in Kamsa's heart. It was that minute that Kamsa knew that he was going to become the king of all the Yadavas. No matter what.
(Banasura has a very long timeline. He was the son of Bali, the asura. So it meant that he was alive from the times of Bali to Kamsa and even after that, which was not surprising. What makes his character so interesting is his boon from Lord Shiva. Because of the boon from Lord Shiva, Banasura caused a war between Krishna and Shiva! Krishna attacked Banasura's kingdom to save his grandson Annirudha. Shiva being on the side of Banasura fought off Krishna's attack.)
It is believed that Jarasandha brought over a part of his powerful army to Mathura as escorts to the Princesses Asti and Prapti, who were to get married to Kamsa.
Kamsa wasted absolutely no time as he used the cover of the army and imprisoned his father. (It was believed that this was done within the palace and even the public were not aware of this takeover.)
Using the army, Kamsa crowned himself as the king of Mathura and started annexing kingdoms.
It is said that with Jarasandha's army, Kamsa had become so powerful that Kamsa was even able to defeat the Devas in battle.