Dragon's Mirror is a Normal 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, Dragon's Mirror is Unlimited.
YGOPRODeck lists Dragon's Mirror for these formats: Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Dragon's Mirror appears in Cybernetic Revolution (CRV-EN040) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Dragon's Mirror is about $0.18 on Cardmarket (prices change frequently).
