Cannot be Normal Summoned/Set. Must first be Special Summoned (from your hand) by banishing 1 FIRE monster from your GY. If this card destroys an opponent's monster by battle and sends it to the GY: Inflict 1500 damage to your opponent.
Rulings
Individual Card FAQs
When "Inferno" battles with another monster with equal ATK, "Inferno"'s effect is not activated because it must destroy the other monster "and send it to the Graveyard", and at that time, Inferno is no longer on the field to activate its effect.
If "Inferno" attacks a face-down "Cyber Jar", "Inferno" is destroyed by the effect of "Cyber Jar" and "Inferno"'s effect is not activated.