Majesty's Pegasus is a Field 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, Majesty's Pegasus is Unlimited.
YGOPRODeck lists Majesty's Pegasus for these formats: Duel Links, TCG, OCG, Master Duel.
Majesty's Pegasus belongs to the Majespecter archetype—use that tag when searching for engine pieces and tech options.
A listed print of Majesty's Pegasus appears in Dimension of Chaos (DOCS-EN058) at Super Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Majesty's Pegasus is about $1.70 on eBay (prices change frequently).
