It changes into a creature even if the spell is countered.
2004-10-04
It triggers when the spell is cast, which means it becomes a creature before that spell resolves.
When an opponent casts a spell, if this permanent is an enchantment, it becomes an Illusion creature with power and toughness each equal to that spell's mana value.
If the spell is no longer on the stack when the triggered ability resolves, the mana value of the spell is still remembered.
When it turns into a creature, it is no longer an enchantment.
