Parshurama was the son of the sage Jamadagni and his wife Renuka.
There are lots of stories about Parshurama. He is known as the Brahmin who had vowed to wipe the earth of all Kshatriyas and had done so twenty one times.
In the Mahabharata, this ancient Brahmin warrior, did not actually take part in the great war, but all the main protagonists in the war had directly or indirectly been influenced by his teachings,
The Kaurava army had five successive commander-in-chiefs during the eighteen days of war.
Day 1 to 10 – Bheeshma (a direct disciple of Parshurama)
Day 11 to 15 – Drona (a direct disciple of Parshurama)
Day 16 to 17- Karna (a direct disciple of Parshurama)
Day 18 Shalya (do not know who is Guru was)
Day 18 Ashwathama (a disciple of Drona, who was a disciple of Parshurama)
The Pandavas had one commander in Chief for all the eighteen days of the war, Dhrishtyadhumna, who was a student of Drona, who in turn was a student of the great Parshurama.
Besides the main protagonists, the hundred Kurus on one side and the five Pandavas on the other side, were all students of Drona too.
Thus Parshurama, the ancient warrior indirectly played a huge part in the great war of the Mahabharata.