Enchantment, 1G (2)
Rare
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.
Illus. Berry

10/4/2004: When it turns into a creature, it is no longer an enchantment.
10/4/2004: Does not trigger on lands put onto the battlefield by a spell or ability.
8/1/2008: A noncreature permanent that turns into a creature is subject to the "summoning sickness" rule: It can only attack, and its {T} abilities can only be activated, if its controller has continuously controlled that permanent since the beginning of his or her most recent turn.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander