Penance of Lord Shiva - Vamana Purana Part-13

Lord Shiva was so deeply attached to Uma that for 1000 years, he was possessed by only her thoughts. He forgot about his duties and as a result, there was anarchy all over the world. His obsession with Uma had also decreased his radiance. He decided to do penance with the objective of regaining his radiance.

When Uma came to know about his decision, she was unhappy but Lord Shiva consoled her by relating the significance of his decision. Before leaving, he entrusted the responsibility of her security to Nandi. He started wandering in search of a suitable place for doing penance. Sometimes, he did penance under the tree, sometimes on the mountain peaks and sometimes on the banks of a river. Initially, he used to eat only kand and Moola but later on he stopped eating even that and lived only on air. This way, 900 years passed during which he travelled to all the three lokas.

Lord Kartikeya kills Demons Taraka and Mahishasura - Vamana Purana Part- 12

BIRTH OF KARTIKEYA

Swallowing of Lord Shiva's sperm had subdued Agni's radiance. The deities advised him to take Lord Brahma's help. While he was on his way to Brahma loka, he came across a river named Kutila and requested her to hold Shiva's sperm. 

She agreed and requested him to release it in her waters.

In course of time, she became pregnant. The thought of giving birth to an illegitimate child tormented her, so she went to Lord Brahma to take his advice. Lord Brahma instructed her to abort her foetus at Udyachal Mountain, which was covered by the dense forest of reed. Lord Brahma felt that it was a very safe place for her and nobody will be aware of this incident. Kutila followed his instructions.

Kutila aborted her foetus just according to Lord Brahma's instructions. The foetus remained there for 10,000 years after which a child was born, radiant like a rising Sun and eyes like the petals of lotus flower. The child being hungry started to cry. At that time, all the six Kritikas were passing through that forest. They were so mesmerised by the child's beauty that they started quarrelling among themselves as to who should first feed breast milk to the child. Seeing their quarrel, the child appeared with his six heads. This way, all the six Kritikas fed their breast milk to the child at a time. This is the reason why Kartikeya has six heads.