Definition of Kartikeya:
Kartikeya is the god of war. He directs the Gana that form the army of his father, the god Shiva Kartikeya is represented with six heads.
The origin of its six heads comes from the myth in which Shiva threw six sparks of fire from his eyes into Lake Sarvana, where they became six children who were raised by the Rishis. When the goddess Parvati saw the children, she was captivated by their beauty and gave them a hug of such magnitude that they merged into one body, even so they kept their six heads.