Backdrop for the story - End of Yadavas

References:
The Mahabharata of Krishna-Dwaipayana Vyasa, BOOK 16, Mausala-parva; Translated into English Prose from the Original Sanskrit Text by Kisari Mohan Ganguli [1883-1896] http://www.sacred-texts.com/hin/m16/m16000.htm

Setting of the plot:

After the great Mahabharata war (circa 3031 BC), Krishna & Balaram return to Dwaraka and rule on for 36years. There are several small kingdoms (clans of yadavas) under them such as Bhopas, Vrishnis, Satyakis, Kritavarmas, etc...During this time as the Yadavas get more powerful and inevitably more arrogant and drunk with power, they fail to discharge their Kshatriya duties properly. One day, led by Krishna's son Sambha, they play a practical joke on a Rishi and he incurs a curse whereby a mace would be born to him and that would prove to be all of their death-knell.... They dont take it seriously, but soon, Sambha develops labour pains and delivers a mace!!! The people get scared and wondering what to do, the chieftains decide to powder the iron mace and throw it in the ocean. Thinking that ended their misery they continue to be as only they can be.... proud, quarrelsome, arrogant.... However, the powder sunk in ocean gets washed ashore (near present day Prabasha Pathan) and grows into dense strange looking plants/shrubs.... Soon, one things leads to another, there is a quarrel of ancient family feud and soon they all start fighting each other, eventually destroying & killing each other.... Krishna & Balaram, seeing this, try desperately to bring peace but of no avail decide their purpose in this kali-yug has come to an end, and end their lives... Balaram just walks into the ocean, whereas Krishna walks to a forest a deranged old man and when asleep a hunter mistaking him for an animal kills him....Arjuna who came to help arrived late and took away the remaining Yadava refugees back to Mathura where, later, he installed Vajranabhi (son of Aniruddha, grandson of Pradhyumna, great grandson of Krishna) as the ruler of Yadavas.

But what role does Vajranabhi play? Is there a remedy for the powerful combination of Gandhari and the Rishi's curse? Are future Yadavas safe. Our story takes off from there and fast forwarded 5000 years to present day (Circa 21st AD).