Unity 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, Unity is Unlimited.
YGOPRODeck lists Unity for these formats: OCG GOAT, Duel Links, Edison, TCG, OCG, Master Duel.
A listed print of Unity appears in Shonen Jump May 2006 subscription bonus (JUMP-EN006) at Ultra Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Unity is about $1.98 on eBay (prices change frequently).
