Angkor Wat's marvelous bas relief - Battle of Lanka

Hindu mythology is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Indian mythology.

Lanka (Sanskrit: ???? lanka, means "island") is the name given in Hindu mythology to the island fortress capital of the legendary king Ravana in the great Hindu epics, the Ramayana and the Mahabharata; it is also the ancient name of present-day Sri Lanka. The fortress was situated on a plateau between three mountain peaks known as the Trikuta Mountains. The ancient capital city of Lanka is thought to have been burnt down by Lord Hanuman.

After Ravana was killed by Lord Rama, Ravana's brother Vibhishana ruled the kingdom. His descendants ruled the kingdom even during the period of the Pandavas. As per the epic Mahabharata, the Pandava Sahadeva had visited this kingdom during his southern military campaign for the Rajasuya sacrifice of Pandava king Yudhisthira.

Lanka was originally ruled by a Rakshasa named Sumali (as per Ramayana). Later it was taken by Visarvana (Kubera) who was a Yaksha. From him, Rakshasa Ravana, took the rulership of Lanka. Rama killed Ravana and installed his brother Vibhishana on the throne of Lanka.

According to Mahabharata, Yaksha king Vaisravana alias Kubera was the ruler of Lanka. His capital was guarded by Rakshasas.His cousin Ravana fought with Kubera in battle and obtained the sovereignty of Lanka from him. Ravana ruled Lanka as the king of Rakshasas. Having slain the king of the Rakshasas, viz Ravana, with his brother Kumbhakarna, and sons and kindred, Rama installed in the kingdom of Lanka the Rakshasa chief, Vibhishana, pious, and reverent, and kind to devoted dependants.

Rama's invasion and conquest of Lanka

According to the story set forth in the Ramayana and (in an abbreviated version) in the Mahabharata (Book III: Varna Parva, Section 271 ff.), Ravana was a powerful king in Lanka who ruled Lanka as well as reasonable area in India. Laxman who was Rama's brother cut off Ravana's sister Surpankha's nose when she was going to assault Sita. To avenge this, Ravana captured Sita and carried her off to his fortress in Lanka.

Many of the references to Lanka in the Mahabharata are found in sage Markandeya's narration of the story of Rama and Sita to king Yudhishthira, which narration amounts to a truncated version of the Ramayana. The references in the following summary are to the Mahabharata, and adhere to the following form: (book:section). Markandeya's narration of the story begins at Book III (Varna Parva), Section 271 of the Mahabharata.

Sahadeva's expedition to South
The son of Pandu, viz. Sahadeva, conquered the town of Sanjayanti and the country of the Pashandas and the Karanatakas by means of his messengers alone, and made all of them pay tributes to him. The hero brought under his subjection and exacted tributes from the Paundrayas (Pandyas) and the Dravidas along with the Udrakeralas and the Andhras and the Talavanas, the Kalingas and the Ushtrakarnikas, and also the delightful city of Atavi and that of the Yavanas. And, He having arrived at the seashore, then dispatched with great assurance messengers unto the illustrious Vibhishana, the grandson of Pulastya and the ruler of Lanka (2:30).

Presence in Yudhisthira's Rajasuya
Lanka king is listed as present in the conclave of kings present in Pandava king Yudhisthira's Rajasuya sacrifice.

..the Vangas and Angas and Paundras and Odras and Cholas and Dravidas and Andhakas, and the chiefs of many islands and countries on the seaboard as also of frontier states, including the rulers of the Sinhalas, the barbarous mlecchas, the natives of Lanka, and all the kings of the West by hundreds, and all the chiefs of the seacoast, and the kings of the Pahlavas and the Daradas and the various tribes of the Kiratas and Yavanas and Sakras and the Harahunas and Chinas and Tukharas and the Sindhavas and the Jagudas and the Ramathas and the Mundas and the inhabitants of the kingdom of women and the Tanganas and the Kekayas and the Malavas and the inhabitants of Kasmira...