He is the king of hell who says that he is the body which is hell itself. He is Narayana who ascertains who Naraka is, and destroys him with His vision of wisdom, Jnana Drishti. That is the auspicious day of Narakachathurdasi.
Venba:
நரக வுருவா நடலை யுடல கிரக மகமெனவே கெட்ட — நரகனாம் மாயா வியைநாடி மாய்த்துத்தா ணாயொளிர்தல் தீபா வளியாந் தெளி.
The false belief that this hell-like house called body is me, is Naraka himself. To destroy that false belief and let the self shine as Self, is Dipavali.