Mystic Box 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, Mystic Box is Unlimited.
YGOPRODeck lists Mystic Box for these formats: OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Mystic Box appears in Duel Terminal 2 (DT02-EN095) at Duel Terminal Normal Parallel Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Mystic Box is about $0.10 on Cardmarket (prices change frequently).
