Inspiration 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, Inspiration is Unlimited.
YGOPRODeck lists Inspiration for these formats: Duel Links, Speed Duel, Common Charity, TCG, OCG, Master Duel.
A listed print of Inspiration appears in Battle Pack 3: Monster League (BP03-EN232) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Inspiration is about $0.03 on Cardmarket (prices change frequently).
