Power of the Guardians is a Equip Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Power of the Guardians is Unlimited.
YGOPRODeck lists Power of the Guardians for these formats: Duel Links, TCG, OCG, Master Duel.
Power of the Guardians belongs to the Guardian archetype—use that tag when searching for engine pieces and tech options.
A listed print of Power of the Guardians appears in 2018 Mega-Tin Mega Pack (MP18-EN208) at Super Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Power of the Guardians is about $1.44 on TCGPlayer (prices change frequently).
