The story of the second Mahabharata war is mentioned in Bhavishya Purana Pratisarga parva. It is the third parva among five parvas. The total story of the second Mahabharata comprises of 32 chapters.
This parva begins with sage narrating Suta an event from Mahabharata. After the end of the Mahabharata war, Sri Krishna prays to Shiva and asks him to protect the Pandavas camp.
I praise the Rudra who is pleasant, who is bhutesha (ghost dweller), builder of time, who sees every welfare of living being and sin destroyer, I praise you again and again. Bhagwan! Please protect Pandavas, they are my bhakts and they fear time.
Hearing this prayer, Shiv Jee carrying his Trishula (trident) rode on his Nandi and came to protect Pandava’s camp. At that time Krishna was away to Hastinaapur by the order of Yudhisthira and Pandavas were living on the banks of Saraswati River.
At mid-night, Ashwatthaamaa and Kritvarmaa and Kripaachaarya came to
Pandavas camp and they pleased Shiv by their prayers. At this Shiv allowed them to enter Pandavas camp. Mighty Ashwatthaamaa killed Dhrishtdyumn etc
warriors by the sword given by Shiv and then went back with Kripaachaarya and
Kritvarmaa. Only one Soot remained there who informed Pandavas about this
killing. Bheem etc Pandavas thought this the act of Shiv Jee and they got
extremely angry and started fighting with Shiv Jee. Whatever weapons were used by them at Shiva jee, they all entered his body. After that seeing this, with anger they all started beating Lord Shiva with fists and arms. At this Shiv said - Because you are all the devotee of Shree Krishna that is why I am protecting you otherwise you were all worth of being killed. You all will have to suffer for this by taking birth in Kali Yug.” and he got disappeared.
Pandavas got very sorry at this, They came to Krishna for help. All of them prayed Shiv jee and Shiv asked them to ask for Var.
Krishna said - “Dev, Whatever weapons of have entered in your body, please return to them and free them from Shaap (scarce).”
Shiv ice said “Krishna, I salute you. At that time I was deluded by your Maya that is why I gave Shaap to them. Although my words will not be a lie, still Pandavas and Kauravas will be born on Prithvi (earth) from their part and will be free soon. Yudhisthira will be the son of Vats Raaj (Bacchraj), his name will be Baalakhaani (Maalkhan) and he will the king of Shireesh (Sirsa) city. Although, he spoke bad languages, Bheem's name will be Veran and he will be the king of Vanaras (Benaras). Whoever will take birth from Arjun's part, he will be my Bhakt and great intelligent. He will be born In Parimala’s house and his name will be Brahmaananda. Nakula will be born as Ratnabhaanu (Raatibhaan)’s son in Kanyakubja and his name will be Lakshmana. Sahadev will be the son of Bheem Sinh and his name will be Dev Sinh. Dhritraashtra’s part will be born as Prithviraaj in Ajmer and Draupadi will be born as Velaa, the daughter of Prithviraaj. The great donor Karna will be born as Taaraka (Saadar/Tahaar). At that time I will also take Avatar in the form of Raktabeeja. Kauravas will be skilled in Maya war and Pandavas will fight according to Dharma.”
Krishna and Balarama also took form to fulfil the boon to Kali. Kali prays to Krishna because his sons are destroyed and he has no place to dwell. Krishna approves that boon.
“Kali said: - My sons who belonged Mlecchas, had been came in order of Arya
dharm. Swamin! For me create a four rooms, - in first room will be for gambling (dyuta), second place where people will drink wine, third place where lots of gold will be stored and fourth place where women will come and have a refreshment of laughing. This all were destroyed by the Kshatriyas of Agnivamsas. Janardaan! I have come here leaving every time, body, family and nation. And now I’m situating now in your feet.”
Then with a smile, Bhagwan Krishna said:-”Kale (Kali). For your protection, I will take birth in this earth, who will be strongest. My ansh (part-avatar) will reach the earth and destroy those strong kings ruling now and will restore kings belonged to Mlecchas dynasty in the nation.
So, according to pratisarga parva, these are the incarnations from Mahabharata:
- Krishna - Uday Singh (Oodal)
- Balaram - Aahlad
- Shiva - Raktabeeja
- Yudhishtira - Balakhani
- Bheema - Veran
- Arjuna - Brahmaananda
- Nakula - Lakshmana (son of Ratna Baahu)
- Sahadeva - Dev Singh
- Draupadi - Vela (daughter of Prithviraj chauhan)
- Dritharashtra - Prithviraj Chauhan
- Karna - Taraka
- Duryodhana - Mahipati
- Shikandi - Roopana (son of Desh raaj)
- Drupada - King Parimala
Apart from these, some of the Kauravas took birth as sons of with the same names namely- Dussaha, Dushala, Jalasandha , Samah, Saha , Vinda , Anuvinda, Subaahu, Dushpradharshan, Durmarshan , Dushkarna , Somakeerti , Andur , Shal, Satva and Vivitsu.
The final war took place for the eighteen days similar to the Kurukshetra. The war takes place between many kings but the main war is between amshas of the Kauravas and Pandavas but Mahi pati who has part of Duryodhana was aided by Mlechha king Sahoddina who once defeated Prithviraj.
The battle took place in Kurukshetra. The camps of Pandava amshas were set at Samantha Panchaka and Kauravas placed their camps at the coast of river Ganges. From chapter 32:
After they had arrived at the place, they saw Brahmaananda indulged into deep meditation to that pèous teerth place named Samanta Panchaka. There those part of Pandavas put their military camps. And on the cost of the river Ganges, those part of mighty Kauravas who were desired for victory set up their camps. On the month of Kartikaa-Shukla, the day of full moon, they performed pious bath and did charity. After that on the month of Maargsheersh
(Agahan). the day of Krishna Dwitiya, that furious battle started where, the
dynasty of Bishwaksenas king Lahara came with his sixteen sons, who were taken birth from the part of Kauravas.
The book Rethinking India's Oral and Classical Epics: Draupadi Among Rajputs, Muslims gives more details and analyses the part of this Pratisarga parva how the characters of the second Mahabharata relates with the original Mahabharata.