Discarding your hand is a cost to Normal Summon or Set this card. It will not activate the effect of a card like “Goldd, Wu-Lord of Dark World”.
You must have at least 1 other card in your hand, besides “Infernal Incinerator”, to discard when your Normal Summon or Set “Infernal Incinerator”.
This card can be Special Summoned (even from your Deck, with a card like “Monster Gate”). You do not have to discard your hand when you Special Summon this card.
When you Normal Summon or Set “Infernal Incinerator”, it does not start a chain even though you are using the monster’s effect to do so.