Adishakti created Trinity of Gods (Brahma, Vishnu and Shiva) and Goddesses (Saraswathi, Lakhsmi and Parvati) for balance of this supreme universe.
Universe creation is never with single attribute but coexistence of
- Dharma & Adharma,
- Good & Bad,
- People with Deva & Demon qualities,
- True and False,
- Positive & Negative to counter the other.
It would have been the ideal world if the entire universe happens to be filled with Dharma, Good, People of Deva qualities, True, Truth and Positiveness only!, but its not so.
Time to time when the Negative forces increase God takes various manifestations, Avatarams (Avtars) to save mankind from the perils.
Lord Vishnu has Das(h)avataram (Ten Avtars)
Ganesh – Son of Shiva, remover of Obstables and god of beginnings
Hanuman – is a Devotee of Lord Rama (Vishnu avtar)
Ayyappa (Sasta) – is Son of Hari (Mohini avatar of Vishnu) & Hara – god of victory and success.