Ram Katha: It is described in Anand Ramayana that Lord Ram visited Lanka twice after returning to Ayodhya to protect Vibhishana. Anand Ramayana (Rajya Kanda, Chapters 4–7), talks about a city named Mayapuri on the banks of the Shrona River. When, Vibhishana was defeated by the mighty Poundraka, he went to Lord Ram and narrated his entire story. Upon hearing the sorrowful tale of his friend, Ram and Sita went to Lanka with him. They defeated Poundraka and then enthroned Vibhishana in Lanka before returning to Ayodhya.
When Vibhishana talked about Kumbhakarna’s son:
One day, while Lord Ram was seated in his assembly, Vibhishana, with his wife, son, and ministers, sat with a humble demeanor and requested protection. Narrating the story of Kumbhakarna’s son, Vibhishana said that many days ago in the original constellation a son was born to Kumbhakarna, who was sent to the forest, where honeybees protected him by dripping drops of honey into his mouth. When he heard from people that Ram had annihilated his father and their kin, he, through intense penance, satisfied Brahma and obtained a boon that he would only die at the hands of a woman. Filled with pride due to the boon, he ascended Lanka with the help of demins residing in the netherworld. Vibhishana fought against him for six months and in the end, he defeated him and established control over Lanka.
In this situation, Vibhishana fled in the middle of the night with his son, wife, and ministers through an underground passage and reached Ayodhya in Ram’s presence. The Rakshas born in the original constellation, nurtured under the trees, was called Moolkasura. Hence, people referred to him as Moolkasura. During the battle, he had once told Vibhishana that after conquering Lanka, he would go to Ram, who had destroyed his father and their lineage. After that he will liberate himself from my ancestral debt.
Lord Ram made a plan to kill Moolkasura:
Upon hearing Vibhishana’s current situation, Ram was greatly astonished and instructed Lakshman to send messengers to summon all the kings in the world. Lakshman sent messengers as per Ram’s command and the messengers quickly returned completing the task. Deciding on this, Ram, along with his vast army and brothers like Lakshman and Bharat, left Ayodhya to slay Moolkasura at an auspicious day and moment. He also took Lav and Kush along. On the way, the kings who were followers of Ram met him with their respective armies. Ram accommodated all of them in the Pushpaka Vimana.
During this journey, Sugriva came with eighteen groups of monkey soldiers and Ram seated them too. After leaving Sita behind, Ram boarded the Vimana. While flying through the sky, observing many countries through the celestial route, they advanced towards Lanka and quickly reached the designated location. Meanwhile, upon hearing this news, Moolkasura, armed with a crore-strong army, arrived outside Lanka’s battleground to engage in battle with Ramchandra. At that time, due to Brahma’s boon, he was exceedingly arrogant. The demon army began striking the monkey troops who in turn retaliated by attacking with chunks of mountains and large trees. In this way, a fierce battle between the two armies continued for seven days.
In that battle, whenever any monkey was killed, Hanuman Ji would bring the Sanjeevani herb from the Dronachala mountain and revive them. Three-fourths of the demon army was annihilated, and the rest were defeated. When Moolkasura saw that only a few demons were left, he became furious. He sent his ministers, generals, and remaining forces to fight.
Meanwhile, when Ram’s army saw that more demon forces were approaching and they were overwhelming them with their swords, they, too, began a fierce battle, wielding large rocks and trees. In a short time, the enemy’s ministers, generals, and forces were sent to the abode of Yama.
When Moolkasura heard that his army had been decimated, he became enraged. He mounted a divine chariot and, with a small army, set out to fight. Seeing the kings allied with Ram ready to fight, he entered the battlefield. The kings, observing him prepared to fight, also joined the battle. They launched a barrage of arrows at the demon, accompanied by the thunderous roar of drums. However, Moolkasura incapacitated them all in no time.
Witnessing the kings unconscious, as per Ramchandra’s orders, ministers such as Sumantra went with their respective armies to fight. When they too fainted, young boys like Kush went forward to fight. Seeing the arrival of Kush and others, a fierce battle ensued.
After some time, Kush lifted Moolkasura with his arrows and threw him outside Lanka. However, he immediately got up, mounted his chariot, and entered a cave with the desire to obtain powerful weapons and a chariot. There he engaged in activities according to the rituals of a celibate. When Vibhishana saw the smoke of the ritual, he went to Ramchandra, sitting under the Kalpavriksha tree with his brothers, and said, “Oh Ram! He is performing a ritual in a cave. Therefore, send the monkeys again. If the ritual is completed, he cannot be defeated by anyone.”