A summary of the relevant portion:
The Pandavas are staying in Sage Vishnuchitta's ashrama when the Dushta Chathushtaya plan the destruction of the Five. On Duryodhana's orders, a sage who wears lots of vibhuti (Dhoola-Mamuni) brings to him Kaala-MaMuni. Duryodhana falls at his feet and says in flattering terms: "Thanks to your tapasya my reign extends over the earth and my orders are followed. Do see to it that I am saved from a danger that threatens me." Sage Kaala MaMuni, an expert in Shastras wants to know why he has been invited. Duryodhana looks at Sakuni who says: "Rid this Duryodhana of his fierce enemies." The terrible sinner (ak-kodum-paavi) who gains fame by his charity on this earth, Karna, chips in: "If the Five continue to live, they will ask for the earth again as it has been released from the effects of the dice game. If you can perform a homa to kill them in ways the enemies do not know of, you would have gifted this seven-islanded earth to the snake-bannered Kuru."
Hearing Karna's words, Sage Kaala MaMuni shudders and thinks all his good karma gathered during his seven births past and his tapasya in this birth are at an end. He bursts out:
"Your unsurpassed fame
is spread in the eight directions.
There is no direction
which does not sing of your fame.
The earth is resting safe
Under your umbrella
Presenting a life for people
According to Manu dharma.
Why did you think
Of this terrible act?
One who wears anklets!
Even if I perform this homa
To send the Pandavas
To Death's regions above,
Will the imperishable
Pandavas die?
The evil work if I begin
Listening to your command,
Will only destroy me
And will not affect the Pandavas
Who are victorious lions.
They have Mayavan with them.
To assent to your request
Who wants to own the earth
So vast, I will have to die
As those who commit suicide
By consuming poison.
This alone will happen."
(verses 9 & 10, translated by Prema Nandakumar)
But the Dushta Chathushtaya (Duryodhana, Duhshasana, Sakuni, Karna) praise the sage no end and pray to him and he agrees in sheer desperation, giving a list of things needed. He sets up a corner of his Ashrama for performing the abhicara homa, and Villiputturar gives a suitably terrifying picture. Kaala MaMuni offers sacrifices that terrifies men and gods and raises a fire in a huge pit with wood taken from trees that have a way of growing up with bends, the flames shooting to the skies. He recites Vedic mantras and pours ghee into the fire (each mantra gets seven sruvas {wooden ladle} of ghee). A huge ghoul like a dark mountain now comes out of the fire. Its eyes spout fire while its terrifying tusks are white like moonlight. The sage shudders.
By now Yama learns of the abhicara homa and prepares to save the Pandavas as he is one who is bound only by Dharma. So there is a scene-shift. In the place where Pandavas are camping, a deer takes away the deerskin of a brahmin boy. On a complaint lodged by the boy, the Pandavas pursue the deer. They get tired following it and come near a poison tank. Actually it is Yama who has become the poison tank and the tree nearby. Dharma sends Sahadeva to get water from the tank. Sahadeva dies on tasting the water. The same thing happens to Nakula, Arjuna and Bhima. Bhima writes on the sand, "the water is poisoned" before he dies. Dharma swoons with thirst and the worry that his brothers have not yet returned.
There is a scene shift again. The ghoul that had come out of the abhicara homa asks Kaala MaMuni for orders. On being told that it should kill the five Pandavas, the ghoul says it will go in search of the Pandavas who are yet not seen by it. But should they be found missing, it would return to kill the sage himself. The ghoul searches around in the forest and comes across Dharma who is in a swoon. The ghoul feels that the Pandava must have died unable to bear the heat of the forest and further search reveals to it the four dead brothers. The ghoul actually feels sad that such a terrible fate has overtaken the Pandava brothers. Incensed that his targets are already dead, the ghoul returns to Kaala MaMuni, screams at him for asking him to kill people who are already dead (the god-like sage should have known it, having trikaal-drishti kaalamkal moonrum ennum katavul nee), laughs angrily and beheads him with his tri-sul. The ghoul then returns back to the homa fire.
There is now another scene-shift where we see Dharma coming back to senses, searches for the brothers and sees them dead on the banks of the poison tank, reads Bhima's message, tries to drink the water, is stopped by a disembodied voice that asks questions. Immediately after Dharma answers its questions, Yama appears and teaches Dharma a mantra to raise a brother and Dharma prefers Sahadeva and explains to Yama why he did so in preference to Bhima and Arjuna, gains further mantras from the pleased Yama who also tells his son of the abhicara homa performed by Duryodhana. Yama then blesses him and withdraws.
Incidentally, Arjuna's tapasya and Mookasura-vadha etc form the first sarga (Arjunan Tavanilai Sarukkam) of Aranya Parva and the Poison-tank episode the last Sarga (Nacchu-poykai Sarukkam) in Villipputturar's Bharatham.