Nishada Kingdom :

Nishada is the name of a tribe mentioned in ancient Indian literature (such as the epic Mahabharata). The ancient texts mention several kingdoms ruled by this tribe. In the Mahabharata, Nishadas mentioned as tribes that have the hills and the forests their abode. They are linked with a king called Vena who became a slave of wrath and malice, and became unrighteous. Brahmanas slew him. Some of Vena's descendants became Nishadas and some others were called Mlechchhas, who resided on the Vindhya mountains.

Ekalavya was an archer of a Nishada tribe. 

Identity :

In the earliest of the Indo-Aryan texts, the term "Nishada" may have been used as a generic term for all indigenous non-Aryan tribes rather than a single tribe.This is suggested by the fact that according to Yaska's Nirukta, Aupamanyava explains the Rigveda term "pancha-janah" ("five peoples") as the four varnas of the Indo-Aryan society and the Nishadas. The Nishadas are sometimes confused with the Nisadhas who were a distinct, Indo-Aryan tribe that lived in a country called Nisadha.

Physical appearance :

The Shanti Parva of the Mahabharata describes the Nishadas having dark skin colour similar to that of charred wood, black hair, blood red-coloured eyes, and short limbs. The later texts such as the Vishnu Purana and the Vayu Purana also emphasize the dark skin colour of the Nishadas. The Bhagavata Purana mentions the Nishadas as having copper-coloured hair, high cheekbones, and low-tipped nose.

Occupation :

Various ancient texts associate the Nishadas with hunting and fishing. Nishadas are presented as hunters in the Bala Kanda of the Ramayana, Utpala's 8th century commentary on the Brihat Samhita, and the Dharmasutras of Vaikhanasa and Ushanas. The Adi Parva of the Mahabharata describes the Nishada prince Ekalavya as the son of an archer, which suggests that archery was a hereditary trait of the Nishadas.

The Raghuvamsha presents the Nishada as boatmen. The Ayodhya Kanda of the Ramayana, which mentions the Nishada as the name of an occupational caste (jati), states that the Nishada king helped Rama cross the Ganges River. The Harivamsha states that the Nishadas collected gems and jewels from the river beds.

Maskarin's commentary on Gautama Dharmasutra suggests that elephant-training was another occupation associated with the Nishadas. This is also corroborated the use of the term "Nishadin" to describe an elephant-keeper in Bana's Harsha-charita and Magha's Shishupala-vadha.

Relations with the early Indo-Aryans :

The Nishadas appear to have been among the first indigenous tribes encountered by the Indo-Aryans in India. Most of the other indigenous tribes find few mentions in the Vedic texts, and generally appear as victims of the Indo-Aryans. However, the Nishadas appear in these texts several times, and as a full-fledged tribe within the Indo-Aryan social framework. These references suggest that the Indo-Aryans made efforts to assimilate the Nishadas into their own social order, but the Vedic ritual status granted to the Nishadas was limited in nature. Historian Ramaprasad Chanda speculates that the Nishadas were too numerous and too powerful to be eliminated, enslaved, or expelled by the Indo-Aryans: this may explain the limited attempts to assimilate them.

It is possible that only the high-class among the Nishadas were inducted into the Indo-Aryan society, while the majority of them remained unassimilated. Panini's Ganapatha mentions a gotra called Nishada, which according to scholar D. D. Kosambi, suggests that some tribal priests were assimilated as Brahmanas in the Indo-Aryan society.

Social status :

The Rudra Adhyaya of the ancient Yajurveda Samhita shows reverence to the Nishadas, among others. Nevertheless, the Nishadas held a low status in the Indo-Aryan society. The Shanti Parva of the Mahabharata states that the Nishada originated from the pierced thigh of the tyrant king Vena.In what appears to be an attempt to define the status of the Nishadas in the varna system, several ancient texts present them as progeny of parents from different varnas. This appears to have been done for legal purposes, since a person's varna status determined how the contemporary law treated them.
The Anushasana Parva and the Naradasmriti describe the Nishadas as of mixed Kshatriya and Shudra parentage.

Nishada Kingdom of Ekalavya :

Ekalavya was the son of Hiranyadhanus, king of the Nishadas. He came to Hastinapura to join the military school of Drona.

Ekalavya's kingdom was the most famous Nishada kingdom during the time of the Pandavas. This kingdom was visited by Sahadeva during his military campaign to the south, to collect tribute for Yudhishthira's Rajasuya sacrifice;- Sahadeva, the Kuru warrior, conquered the country of the Nishadas and also the high hill called Gosringa, and that lord of earth called Srenimat .

Ekalavya, the king of the Nishadas, always used to challenge Vasudeva Krishna to battle; but he was slain by Krishna in battle . Arjuna had come to Nishada kingdom of Ekalavya, after the Kurukshetra War, to collect tribute for Yudhishthira's Ashwamedha sacrifice. Arjuna proceeded to the dominions of the Nishada king, viz., the son of Ekalavya. The son of Ekalavya received Arjuna in battle. The encounter that took place between the Kuru hero and the Nishadas was furious. Unvanquished in battle, the valiant son of Kunti defeated the Nishada king who proved an obstacle to the sacrifice. Having subjugated the son of Ekalavya, he proceeded towards the southern ocean. 

Nishada Kingdom close to Kalinga and Vanga :

A prince named Ketumat is mentioned as battling along with the Kalingas against Bhima, in the Kurukshetra War. He was mentioned as the son of the Nishada king. He could be the son of Manimat the Nishada king, who was defeated formerly by Bhima. Ketumat was slain by Bhima along with the Kalinga heroes.The Kalinga, the Vanga, and the Nishada heroes, riding on elephants were said to attack Arjuna in Kurukshetra War.

Mekalas (a kingdom close to Dakshina Kosala Kingdom, in Chathisgad) and Utkalas (western Orissa), and Kalingas, and Nishadas and Tamraliptakas (south of West Bengal), were mentioned as advancing against Nakula. The Kalingas, the Vangas, the Angas, the Nishadas and the Magadhas were mentioned together on the Kaurava side.

A Mountain Range named Nishada :

A mountain range in ancient India is named Nishada, mentioned along with other mountains like Meru, Mahendra, Malaya, Sweta, Sringavat, Mandara, Nila Dardurna, Chitrakuta, Anjanabha, the Gandhamadana mountains and the sacred Somagiri.

Nishada as a musical note :

Shadaja, Rishabha, together with Gandhara, Madhyama, and likewise Panchama; after this should be known Nishada, and then Dhaivata. The seven original notes are Shadja, Rishabha, Gandhara, Mahdhyama, Panchama, Dhaivata and Nishada