Complex sentence: According to a legend, the river Ganges, polluted by millions of people bathing in it, assumes the form of a black cow and comes to the Narmada to bathe and cleanse itself in its holy waters.
Split into simpler sentences: According to a legend, the river Ganges is polluted by millions of people bathing in it. To cleanse herself, Ganges acquires the form of a black cow and comes to the Narmada to bathe in its holy waters.