Sea Lord's Amulet is a Continuous 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, Sea Lord's Amulet is Unlimited.
YGOPRODeck lists Sea Lord's Amulet for these formats: Duel Links, TCG, OCG, Master Duel.
A listed print of Sea Lord's Amulet appears in Duelist Saga (DUSA-EN009) at Ultra Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Sea Lord's Amulet is about $0.17 on Cardmarket (prices change frequently).
