Spell Cards that are eligible for this card’s effect include: Set Spell Cards, Equip Spell Cards, or Continuous Spell Cards destroyed by your opponent’s card effects and Spell Cards negated and destroyed by an opponent’s “Magic Jammer”, “Solemn Judgment”, “Horus the Black Flame Dragon LV8”, etc. It also includes Spell Cards discarded from your hand by your opponent’s card effect, like “Delinquent Duo” or “Confiscation” and Spell Cards sent from your Deck to Graveyard by your opponent’s “Needle Worm”, “Don Zaloog”, “Vampire Lord”, etc.
If you activate “Painful Choice” and a Spell Card is included in the 4 cards that are sent to the Graveyard, it cannot be targeted with the effect of “Fairy Guardian” since it was YOUR “Painful Choice” that sent the card to the Graveyard, even though your opponent decided which card you kept.
Netrep Rulings:
The effect of “Fairy Guardian” may only be activated in a controlling player’s Main Phase 1 or Main Phase 2.
Tributing “Fairy Guardian” is a cost to activate the effect of “Fairy Guardian.”