When an opponent casts a creature spell with flying, if this permanent is an enchantment, it becomes a 3/5 Spider creature with reach. (It can block creatures with flying.)
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.
2008-05-01
wotc
The ability only triggers if the creature spell has flying, regardless of whether an effect would cause the creature to have flying once it entered.
2008-04-01
wotc
This card now uses the Reach keyword ability to enable the blocking of flying creatures. This works because a creature with flying can only be blocked by creatures with flying or reach.
2004-10-04
wotc
When it turns into a creature, it is no longer an enchantment.