The Reliable Guardian is a Quick-Play 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, The Reliable Guardian is Unlimited.
YGOPRODeck lists The Reliable Guardian for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of The Reliable Guardian appears in Dark Beginning 1 (DB1-EN028) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for The Reliable Guardian is about $0.02 on Cardmarket (prices change frequently).
