Karkotaka Instructs Nala to Go to Rituparna
Transformed and unrecognizable, Nala receives a clear plan from Karkotaka: go to King Rituparna in Ayodhya as the suta Bahuka, exchange his skill with horses for Rituparna's skill with dice, and use that skill to reclaim his kingdom, his wife, and his children.
Karkotaka, still wearing Nala's form, gave the transformed king his instructions.
"Go from here and say that you are the suta Bahuka. Go to Rituparna, who is extremely skilled in gambling with dice. Leave now for the beautiful city of Ayodhya. In exchange for your skill with horses, that king will give you the skill with dice. That prosperous one, descended from the lineage of Ikshvaku, will become your friend.
"When you have become skilled with the dice, you will ensure your welfare and prosperity. You will be reunited with your wife. Banish all sorrow from your mind. I tell you truthfully that you will obtain your kingdom and your children.
"When you desire your own form back, recall me in your mind and clad yourself in these garments. On wearing these garments, you will obtain your own form back."
He gave Nala two divine garments.
Then the king of serpents disappeared, then and there.
Nala stood alone in the forest — transformed, disguised, carrying two garments that held the key to his restoration. He had a destination now: Ayodhya. He had a name: Bahuka, the suta (charioteer). And he had a purpose: to learn the skill with dice that would let him win back everything he had lost. Aranyaka Parva, Chapter 360