Whenever an opponent plays a land, if Hidden Stag is an enchantment, Hidden Stag becomes a 3/2 Elk Beast creature. Whenever you play a land, if Hidden Stag is a creature, Hidden Stag becomes an enchantment.
2004-10-04
Does not trigger on lands put onto the battlefield by a spell or ability.
2004-10-04
When it turns into a creature, it is no longer an enchantment.
2008-08-01
A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.