System Down is a Normal 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, System Down is Unlimited.
YGOPRODeck lists System Down for these formats: Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of System Down appears in Cybernetic Revolution (CRV-EN041) at Rare rarity.
Among markets shown on this page, the lowest listed snapshot for System Down is about $0.61 on Cardmarket (prices change frequently).
