Explanation:

- Ambubachi: This is a festival celebrated in Assam, not Odisha. It is associated with the Kamakhya Temple in Guwahati and celebrates fertility.

- Chapchar Kut: Celebrated in Mizoram, this is a harvest festival, marking the end of the jhum cultivation season.

- Namsoong: This festival is celebrated by the Lepcha community in Sikkim. It marks the start of the Lepcha New Year.

- Nabakalebara: Celebrated in Odisha, Nabakalebara is a major ritual involving the renewal of the wooden idols at the Jagannath Temple in Puri. This event is steeped in tradition and is considered highly significant in Odishan culture.