When a monster effect is activated while this monster is on the field (Quick Effect): You can negate the activation, and if you do, destroy 1 other FIRE monster in your hand or field. If this card is destroyed and sent to the GY: You can target 1 FIRE Beast, Beast-Warrior, or Winged Beast monster in your GY, except "Fire King Avatar Arvata"; Special Summon it, but it has its effects negated, also it is destroyed during the End Phase. You can only use each effect of "Fire King Avatar Arvata" once per turn.
How to Get
Can negate monster effects.
Special summons a FIRE Winged-Beast, Beast-Warrior, or Beast monster.
Destroys another FIRE monster on the field to use negation effect.
Revived monster is destroyed during the End Phase.
Destroying your own monsters could be used to your advantage particularly with his own archetype. Fire King monsters trigger effects when they are destroyed via card effect which help you gain advantage.
You can revive the Sacred Phoenix of Nephthys and let it be destroyed during the End Phase. Sacred Phoenix of Nephthys' effect would then trigger in the graveyard reviving itself during your Standby Phase and destroying all Spell/Trap cards on the field.
"When a monster effect is activated while this monster is on the field (Quick Effect): You can negate the activation, and if you do, DESTROY 1 OTHER FIRE MONSTER in your hand or field."
Seeing that the second part of the first effect seems mandatory, does that mean you cannot use the negating effect unless you have another FIRE monster in your hand or on the field?