If a face-up "Fire King" monster you control is destroyed by a card effect (except during the Damage Step): You can Special Summon this card from your hand. If this card is destroyed and sent to the Graveyard: You can send 1 FIRE monster from your Deck to the Graveyard.
Look up the Archetype. If they had all their support, it would make more sense. As of right now, there is no sense in ditch Fire Attributes to the Grave unless its for Flame Emperor's effect & no FK card was made with Nephtys in mind. Please remember that. -_-