( The 'd' in this name is pronounced like 'd' in 'den' and 'th' like 'th' in 'thing'.)
Khaandavaprastham was the name of a dense forest that was burnt down by god Agni ( fire god )with the help of Arjuna and Krishna. It was on this occassion that he gave them the famous bow Gaandeevam to Arjuna , the great mace to Bheema and the frightening conch Devadaththam to Krishna .
The reason why Agni wanted to burn the Khaandavaprastham and Indra's preventing him was this.
Once a king named Svethaki performed many long sacrifices for a continuously long period. The huge quantities of ghee poured into the sacrificial fire during those sacrifices made Agni indisposed. He asked Brahma for a remedy. Brahma suggested to Agni to consume the forest Khaandavaprastham which contained several herbs of medicinal value. But, there lived in it a serpent lord Thakshaka, a friend of Indra. Whenever Agni tried to burn down the forest , Indra would come to the rescue of Thakshaka by sending heavy clouds under his control to downpour on the forest to chase away Agni.
Krishna and Arjuna defeated Indra and cleared Agni's way to consume the forest.
Thakshaka was absent then and so he was safe. But his son Asvasena was trying to fly off with his mother
tagged to his tail. Arjuna cut off his tail. That finished the mother. As Arjuna was about to shoot Asvasena himself again, Indra applied a magic on him making the target invisible to him and extricated Asvasena.
Asvasena wanted to revenge his mother's murder and went to Karna. He told Karna that he would remain with him as a serpent arrow , to be shot at Arjuna to kill him, during an expected fight between the two.
A demon named Maya was also struck in Thakshaka's house, but he begged Arjuna for his life. Arjuna saved him and as a gesture of gratitude, he awarded many things to the Paandavas. A majestic magic hall to Yudhishthira, a mace to Bheema and a conche to Krishna and many things more. This hall had been the source of Duryodhana's jealousy later and all the developments that followed.
Thus, the Khaandavaprastham and its burning down gave rise to many catastrophes in the story.
In fact, we see many such subtle twists in the Mahaabhaaratham at many places. One small incident would lead to a complication in future. Such is the fancy of the book .
"After praying to Naaraayana, Nara, Sarasvathi and Vyaasa, then one should read the Jayam."
DEDICATED TO MY DEAR NIECE VYSHNAVI KRISHNA