Becomes a 2000 attack beater during your battle phase.
Special summoning banishes a FIRE monster in your graveyard.
Cannot be normal summoned, making him dead in your hand if you don’t have FIRE monsters in the graveyard.
Since Hazy Flame decks are made up of mostly FIRE monsters, you usually wont have a problem special summoning Spirit of Flames. You can then use him as a beater or as tribute fodder for Hazy Flame monsters.
Can be used in a Fire King deck as they specialize in destroying themselves to search other Fire King monsters from your deck, loading the graveyard with FIRE monsters. After destroying a Fire King monster to special summon Goka the Pyre of Malice from your hand, you can then banish that Fire King monster in your graveyard to special summon Spirit of Flame.
And you just make an overpowered deck a mediocre deck by using a bad card that all it can do is to hurt its consistency. Not to mention shiranui have already a good full extra deck and current xyz are unworthy to use.