It took a while for Arjuna to realize where he was and why he was there. He recognized the people around him, but, not why he was in their midst.
Uloopi spoke. “You have undergone a trial on your life, all for your own benefit. There was a curse on you because of your causing the fall of the grandsire in a battle where you did not face him directly. I heard this from the Vasus who put that curse on you on the shores of the Ganga. I tried to plead with them on your behalf. They said that you would be felled to the ground by the arrows of my (step) son. You would, then, be cleansed of your sin. Please understand that I had to do this for your own benefit. You may pardon me for doing so.”
Uloopis’ words helped Arjuna to recall his fight against his son and he remembered the arrow that had pierced into his heart. He was pleased with the turn of events and said so to Uloopi. Babhruvahana and Uloopi welcomed him into the palace for rest, but, the Pandava refused the offer. He said that he was already under oath (deeksha) which forbade him luxuries. He invited his son, the king of the Nagas, for the horse sacrifice which was gladly accepted by his host. Then, Arjuna took leave of he Nagas.
In the Magadha kingdom
Arjuna was challenged next by the king of Magadha by name Meghasandhi. We may remember the powerful Jarasindha who was killed by Bhima in a duel that lasted several days. This happened much before the Mahabharata war. Krishna had identified Jarasandha as one of the most formidable among the Pandava enemies and contrived of that plan to eliminate him before he posed a threat.
Meghasandhi fouht bravely, but, Arjuna defeated him without much problem. He, then, conveyed the words of invitation from his brother to the king.
The successful completion of the mission
In the last legs of his journey eastwards (from the north) Arjuna had found opposition from the Chedi king whose father, Sisupala, was killed by Krishna at the time of the Rajasooya of Yudhishthira. He was also challenged by the king of hunters, who was the son of the famous Ekalavya. Ekalavya was the gifted archer who had surpassed Arjuna in every feat of archery and Drona had demanded the thumb of his right hand for the lessons (which he Ekalavya had learnt just by observing Drona and his disciples from a distance).
Arjuna by then had reached the eastern border of kingdoms and turned south and finally, to the east. He went westwards last. There, in the land of the Gandhara Arjuna had to face the opposition of the son of Sakuni. The Pandava defeated him easily. At that time the mother of the king appeared on the scene and pleaded with Arjuna for excusing her son for his impudence.
Arjuna had taken the challenge in his stride. He invited the king for the impending horse sacrifice in Hastinapura and proceeded on his journey back home.
The preparations in Hastinapura
Yudhishthira heard about Arjuna’s successful mission from his men posted at various points and was greatly pleased. Exactly a month was left for the date fixed for the sacrifice. He called his other brothers to his side and asked them to start the preparations for the sacrifice in right earnest.