Mahalaya is an integral occasion in the ethos of West Bengal as it marks the ushering of the festive spirit. It has two dimensions, namely, Devapaksha or the prayer which is offered to God and Pitripaksha or the worship and penance of one`s ancestor. Pitripaksha is also known as Shraddha or the ritual in which food is offered with a sense of affection and gratitude. On this day, Hindus pay their respect to their ancestors and this is known as pindadana. On this very day Pitri-paksha ends and the Devipaksha begins. Mahalaya is also the most suitable time for tantric practices and offering to the Goddess Chandi. Occurring every year in autumn or the `sharot kaal,` Mahalaya reminds every Bengali of Durga Puja that commences exactly after seven days. It is believed that the Goddess Durga pays a visit to the earth for a period of four days only.

As per myth, Lord Rama hurriedly performed the Durga Puja shortly before he left for Lanka to save Sita from the clutches of the demon king Ravana. According to the Puranas, King Suratha worshipped the Goddess Durga in the spring season and it is for this reason that Durga Puja was also called as Basanti Puja. Since Rama organised the Puja and prayed the Goddess Durga in the season of autumn. It is known as `Akal Bodhon` or untimely worship. The Puja of Lord Rama to Goddess Durga was regarded untimely since, according to the myths Puja is performed when the Goddesses and Gods are awake and this time is known as `Uttarayan` and Puja is never offered when the Gods and Goddesses take rest and the time is called `Dakshinayan`. On Mahalaya, the beginning of `devipoksha`, the Gods and Goddesses wake up to prepare for Durga Puja.

There is another legend which speaks of the great hero Karna of the Mahabharata, one of the famous epics in Hinduism. When Karna left for his heavenly abode, he was provided with lots of Gold and Silver but no food since he had never practiced any food charity. He, thus, prayed to the God of death and was sent to the earth for only fourteen days to compensate for this deficiency. In all the fourteen days Karna fed the poor and Brahmin and presented oblations of water. Once he returned to the heaven, he was provided with a plenty of food. These fourteen days are observed in the Mahalaya Paksha. There is a belief that the oblation made in this period benefits every departed soul.