The bounteous kingdom of Magadha is rich in fertile plains surrounding the Ganga and Son rivers. The forests of Magadha are home to mighty elephants—a devastating military asset.
The abundance of iron deposits makes this kingdom the biggest exporter of weaponry and armour, while also being a large source of military might. At the heart of this prodigious kingdom is the capital mountain fortress—Girivraja.
The fortress of Girivraja is surrounded by five mountains. Its colossal Cyclopean wall is several feet thick, built all around them. Huge war drums are stationed at their peaks. And with its sheer civilian-to-military ratio, Girivraja is virtually impenetrable. The only way to legally enter it is through enormous stone gates carved directly out of the mountain, past the royal guards that keep unbroken vigils.
Yet the hot springs of the mountain are another story—they make it a relaxing and restful place for warriors all across Magadha, but the steam from the surrounding mountains gives this place a well-deserved dark and dreadful look.
The city of Girivraja is also home to the palace of King Jarasandha—a large, high-security, military command centre, with a wrestling arena and an imperial viewing gallery for the entertainment of the king. As it is meant to be a functional, secure bunker, it lacks the artistic carvings and paintings found in most other palaces in Magadha.
—Recovered and translated from the lost records of the Zhong Tianzhu Guo Ji (The Account of Central India) by Tang Dynasty Diplomat Wang Xuance.
The court of Jarasandha is filled with Brahmin priests, Demon kings Bana and Naraka, and multiple allies from Magadha and other regions. Jarasandha is granting rewards to the Brahmin priests, being a devotee of Lord Shiva. In the middle of the court procession, the King receives a billet supposedly from Kamsa:
Dear King Jarasandha, you have been a valuable ally and a dear friend to me. To strengthen our relationship, I have a proposal: I want to marry your daughters Asti and Prapti. Please be my guest at Mathura to discuss this matter further. - Ahuka-nandana-Kamsa
The military commander stands up in shock and says, "Unacceptable! This lowly prince has the guts to send such an outrageous proposal and not be present here?! Doesn't he understand the hierarchy?! Calling the King over to 'discuss the matter further'! His Majesty will never accept Kamsa as his son-in-law!"
"Don't say that, commander. Kamsa is a strong man, and a loyal ally. I'd happily marry him to my daughters if he had more political weight! But he has also invited me to Mathura. I must go see him in person and reject him after a duel!" says Jarasandha, descending the throne, looking almost excited to fight Kamsa.
"But Your Majesty, Kamsa is the crown prince. Does he not have enough political weight?" asks one of his advisors, seeking clarification on what he meant when saying "more political weight."
"Kamsa may be the crown prince, but the Yadava confederacy may still favour a direct descendant of Surasena," responds another one of his advisors, grinning, almost expecting the question.
"Commander, prepare the chariots! We're headed for Mathura!" Jarasandha roars with laughter.
"Yes, your Majesty!" replies the commander, his expression sour with rejection.
It is past noon in west Mathura when Jarasandha, in his chariot, is passing through the royal enclave—the region of the city reserved almost exclusively for priests, royal advisors, and elite warriors. This area is heavily policed and is away from the busy trade hubs and artisan streets.
Along with the chariot and the horses pulling it are a few royal advisors and a horde of guards and servants, all riding horses—making a total of around fifty people travelling together.
They are stopped in the middle of the rajamarga, which is a three-layered pavement with proper drainage systems and meant especially for chariots and other royal carts. A squad of iron-masked guards stops the chariot midway, followed by the crown prince asking to meet Jarasandha.
"Welcome, King Jarasandha! My dearest friend! I'm sorry to stop you in the middle of the rajamarga. Your Majesty, I've prepared a private meeting room for you, but it can accommodate only a few people. I request you to bring two of your most trusted guards with you this way."
"It'll only be me!" replies Jarasandha with a smirk on his face, confident that he'd win even if they fought.
The private room, lit with torches, has no windows, only a single entry door and openings meant for ventilation on the ceiling. Sitting on a royal red cushioned chair, Jarasandha starts the conversation.
"Son, you have already impressed me twice, by subduing my elephant and then defeating one of my elite military troops," Jarasandha says loudly.
"But I'll give it to you straight: I can't marry my daughters to a crown prince whose throne is not secure," says Jarasandha as he leans back.
Kamsa, almost sure that Jarasandha would say this, replies, "That's exactly the reason I called you! My father hates me, and the Yadava confederacy is sure to favour a direct descendant of Surasena. Your words are nothing but facts—I am a crown prince whose throne is not secure. I want you to help me secure the throne."
"Hahaha," Jarasandha laughs loudly. "And how are you planning to do that?"
Kamsa cuts off Jarasandha's laugh and says, "By overthrowing the King!"
Jarasandha, shocked, leans forward to listen to Kamsa. And as he listens to Kamsa, his smile widens, ending in a devilish laugh.