Reinforcements is a Normal Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Reinforcements is Unlimited.
YGOPRODeck lists Reinforcements for these formats: GOAT, OCG GOAT, Speed Duel, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Reinforcements appears in Duel Terminal - Preview Wave 1 (DTP1-EN019) at Duel Terminal Normal Parallel Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Reinforcements is about $0.07 on Cardmarket (prices change frequently).
