This is when Vishnu decided to assume the form of Mohini yet again, so as to procreate with Shiva. Vishnu explains the entire matter to Shiva and the latter requests to give him a glimpse of Mohini's form. Shiva is overcome with passion on seeing "her" form and unites with her. Lord Ayyappan is born from this union of Hari and Hara. Ayyappan combines the strength of both Vishnu and Shiva and hence, is invincible.