Magic Jammer is a Counter 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, Magic Jammer is Unlimited.
YGOPRODeck lists Magic Jammer for these formats: GOAT, Speed Duel, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Magic Jammer appears in Dark Beginning 2 (DB2-EN074) at Super Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Magic Jammer is about $0.10 on Cardmarket (prices change frequently).
