When Lord Narayana wished to create, he manifested his male form and slept in the ocean of casual water . A lotus appeared from the navel of his male form, in which Brahma Ji appeared. Many incarnations of Lord Vishnu appear from this form of God and the deities also appear from the parts of this form. There are main ten incarnations of God and there are also partial incarnations of lord , twenty-four incarnations in total.
In the Kaumarsarga, the Lord incarnated as four Brahmins named Sanak, Sanandan, Sanatana and Sanat Kumar and he practiced austerity by performing unbroken celibacy.
The second time God assumed the incarnation of Varaha, to bring out the earth submerged in the abyss for the welfare of the whole world. In this incarnation, he helped Brahma Ji in the creation of world by bringing the earth out of the abyss with his might.
In the creation of the sages, God assumed the third incarnation as Devarshi Narada. In this incarnation, he preached the Satvat Tantra. It describes how one gets freedom from bondage through karma.
For the fourth time, he incarnated as Nara-Narayana from the womb of the goddess murthi. In this incarnation, he had done a lot of hard penance by becoming a sage and restraining the mind and senses.
In the fifth incarnation, the lord appeared as lord of the Siddhas Kapil. In this incarnation, he preached a Brahmin named Aasuri, sankhya scripture, which was forgotten over time .
On Anusuya’s seeking of boon , he became Sanatana Lord Dattatreya, son of Anusuya in the sixth incarnation. In this incarnation, God preached Brahm Gyan to Alark and prahlada etc.
In the seventh incarnation god appeared In the form of the yagya from the womb of Prakapati wife of Ruchi, in this incarnation god protected Swayambhu Manu with his son Yam and other gods.
In the eighth incarnation, the lord appeared as Rishabhdev from the womb of Meru, the wife of Nabhi. In this incarnation, God showed the path of paramahansas that is worshipable to all.
On the prayer of the sages, on the ninth time God assumed incarnation as King Prithu. In this incarnation, God exploited all the medicines, which proved to be welfare for all.
At the end of Chakshus Manvantara, when the whole Triloki was drowning in the sea, the Lord took the incarnation in the form of Matsya and protected Vaivasvata, the lord of the next Manvantara.
God had helped the gods and demons by taking the eleventh incarnation as Kachhap, holding Mandarachal mountain on his pit at the time of Samudra Manthan.
At the time of Samudra Manthan, when the gods and demons were , churning the Samudra to get the nectar, the Lord appeared with the nectar as Dhanvantari, it was the twelfth incarnation of the Lord.
Thirteenth time God took the form of Mohini. When the gods and demons were fighting for the nectar after churning of Samudra, the lord in the form of Mohini fascinated the demons and offered the nectar to the deities.
God incarnated as Narasimha for the fourteenth time. In this incarnation, God had teared Hiranyakashipu’s chest with his fingernails to protect his beloved devotee Prahlad.
God was incarnated as Vamana for the fifteenth time. In this incarnation, God went to the sacrificial fire of the Daityaraja Bali and asked for only three steps of land and took all the triloki from him.
When God saw that all the kings had become arrogant and we’re disrespectful to brahmins, then God had for twenty one times made earth devoid of Kshatriyas by taking the sixteenth incarnation in the form of Parashurama.
For the seventieth time, Lord was born by Parashar from the womb of Satyavati as vedavyas. In this incarnation, God divided the Vedas as people had very little memory.
For the eighteenth time, God had taken Ramavatar as a king. In this incarnation, God performed public welfare acts like Setu Bandhan, Ravana slaughter.
In the nineteenth and twentieth incarnation, he was born as Lord Balarama and Shri Krishna. In this incarnation, God had performed many leelas of love and fought many demons. In Kurukshetra, the war of the Kauravas and the Pandavas,he established dharma by taking side of Pandavas. In this war, God also gave knowledge of Gita through his friend Arjuna.
After the beginning of Kali Yuga, God took Buddhaavatar in Magadesh for the twenty-first time to fascinate the guilty demons of the gods.
At the end of Kali Yuga, when only the looters rule the earth, then Lord will emerge as Kalki and will establish religion again.
In the earlier times, when the monster named Hayagriva had gone with the Vedas and the deities had started to suffer, then God had protected the gods by taking Hayagriva avatar.
Adi Purush who is the origin of all incarnations of God is considered incarnation of the formless God.