In order to obtain the Amrit or ambrosia, the Devas of the heavens and the Asuras of the nether world started to churn the Ksheera Sagara or the Ocean of Milk . If the Asuras were to drink it, they would acquire indomitable strength, and the Devas feared there would not be any end to the harm the Asuras would do to them. So, they approached Lord Vishnu. To solve their problem, Lord Vishnu assumed the form of an enchantress, Mohini who hoodwinked the Asuras and managed to distribute the divine drink among the Devas alone. The Devas now became immortal and this made them arrogant.
When the Asuras realized that they had been cheated, they decided to teach the Devas a lesson. One of them, Tarakasura, began to meditate on Lord Brahma. The Lord was pleased over his tapas and appeared before the Asura leader, and asked what boon he wanted.  Let me be immortal!? said Tarakasura.
“No mortal can avoid death”, said Brahma, “so you may ask for anything else”
In which case, please bless me that I shall die only at the hands of a son of Shiva?, said Tarakasura. The boon was granted.
Around that time, Shiva’s consort Dakshayini had ended her life by jumping into the fire at the yaga being conducted by her father, King Daksha. Shiva was beset with uncontrollable grief. He wandered among the peaks of the Himalayas seeking peace to his troubled mind. He then sat in deep meditation.  Meanwhile, Tarakasura led a formidable army of asura’s and challenged the Devas to a fight. The two sides fought a fierce war in which the demons inflicted an inglorious defeat on the Devas. The Devas ran to Lord Brahma for help. Brahma explained to them about the boon he had granted Tarakasura and told them that they would all go to Lord Vishnu for advice and help. So they proceeded to Vaikuntha, the abode of Vishnu.
After listening to the Devas, Vishnu said: “Dakshayini has now taken birth as Parvati, daughter of King Himavan. You must ensure that she is married to Shiva. The son born to them would put an end to the atrocities of Tarakasura”.
On hearing this, the Devas sent Narada as their emissary to Himavan, who was carried away by Narada’s suggestion that Parvati deserved nobody other than Lord Shiva for a husband. Himavan then went up to the Lord who was still in deep meditation. After paying his obeisance to Shiva, Himavan said: “O Mahadeva! Please permit me to send my daughter Parvati to look after your needs and comforts”. There was no response from Lord Shiva, who continued his meditation. Himavan thought, as the Lord had not indicated any objection, he must have accepted his prayer.
So, he went back and sent Parvati to look after Shiva.  She was just waiting for this moment, as she had already started worshiping the Lord in her heart, and she had also listened to Narada’s praise of Shiva. She had, therefore, decided that she would not marry anyone other than the Lord Himself. Parvati lost no time in reaching the presence of Lord Shiva.  She engaged herself in chores like clearing and cleaning the precincts where Shiva was sitting in meditation and gathering fruits and leaves that he liked to eat. Besides, she also sang songs extolling the virtues of the Lord. This daily routine continued without any hindrance or a halt. But Shiva never for once opened his eyes to look at Parvati who, patiently waited for the Lord to open his eyes and take a look at her.
Now, the Devas led by Indra were marking their time to see that Parvati and Shiva were married and Parvati bore him a son. Indra sought the help of Kamadeva, the god of Love. At first, he was not willing to extend any help, but when he realised that his help would benefit the Devas, he agreed.