Mystical Moon 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, Mystical Moon is Unlimited.
YGOPRODeck lists Mystical Moon for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Mystical Moon appears in Legend of Blue Eyes White Dragon (LOB-094) at Short Print rarity.
Among markets shown on this page, the lowest listed snapshot for Mystical Moon is about $0.03 on Cardmarket (prices change frequently).
