Guarded Treasure is a Continuous 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, Guarded Treasure is Unlimited.
YGOPRODeck lists Guarded Treasure for these formats: Duel Links, Common Charity, TCG, OCG, Master Duel.
A listed print of Guarded Treasure appears in Dragons of Legend (DRLG-EN013) at Secret Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Guarded Treasure is about $0.27 on TCGPlayer (prices change frequently).
