Shield Spear 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, Shield Spear is Unlimited.
YGOPRODeck lists Shield Spear for these formats: Duel Links, Speed Duel, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Shield Spear appears in Speed Duel Starter Decks: Match of the Millennium (SS04-ENB27) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Shield Spear is about $0.10 on TCGPlayer (prices change frequently).
