D - Counter 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, D - Counter is Unlimited.
YGOPRODeck lists D - Counter for these formats: Duel Links, Speed Duel, Common Charity, Edison, TCG, OCG, Master Duel.
D - Counter belongs to the Destiny HERO archetype—use that tag when searching for engine pieces and tech options.
A listed print of D - Counter appears in Duelist Pack: Aster Phoenix (DP05-EN029) at Super Rare rarity.
Among markets shown on this page, the lowest listed snapshot for D - Counter is about $0.12 on TCGPlayer (prices change frequently).
