Archetype of Imagination | Magic: The Gathering
Formats Archetype of Imagination is Legal in
Official Oracle Text for Archetype of Imagination
Creatures your opponents control lose flying and can't have or gain flying.
—Prokopios, astronomer of Meletis
Official Rulings for Archetype of Imagination
2/1/2014 : While you control an Archetype, continuous effects generated by the resolution of spells and abilities that would give the specified ability to creatures your opponents control aren’t created. For example, if you control Archetype of Courage, a spell cast by an opponent that gives creatures he or she controls first strike wouldn’t cause the creatures to have first strike, even if later in the turn Archetype of Courage left the battlefield. (If the spell has additional effects, such as raising the power of the creatures, those effects will apply as normal.)
2/1/2014 : Conversely, continuous effects generated by static abilities (such as an Aura that granted the appropriate ability) would resume applying if the Archetype left the battlefield.
2/1/2014 : If you and an opponent each control the same Archetype, no creature controlled by any player will have the appropriate ability.