Startled Awake // Persistent Nightmare

Skulk (This creature can't be blocked by creatures with greater power.)
When this creature deals combat damage to a player, return it to its owner's hand.

Target opponent mills thirteen cards.
{3}{U}{U}: Put this card from your graveyard onto the battlefield transformed. Activate only as a sorcery.

Shadows over Innistrad Remastered

Target opponent mills thirteen cards.
{3}{U}{U}: Put Startled Awake from your graveyard onto the battlefield transformed. Activate only as a sorcery.

Shadows over Innistrad

Target opponent puts the top thirteen cards of his or her library into his or her graveyard.
{3}{U}{U}: Put Startled Awake from your graveyard onto the battlefield transformed. Activate this ability only any time you could cast a sorcery.

Shadows over Innistrad Promos

A sorcery can't be put onto the battlefield and a permanent can't transform into a sorcery. If an effect exiles Persistent Nightmare and then instructs you to return it to the battlefield, it remains face up in exile (unless that effect instructs you to put it onto the battlefield transformed, in which case it returns as Persistent Nightmare). If an effect instructs you to transform Persistent Nightmare, the instruction is ignored.

If you cause a creature to have 0 power or less, use the actual value (which may be negative) to determine whether it can block or be blocked. A creature with skulk and 0 or less power most likely won't be blocked, but it won't deal combat damage and won't trigger any abilities that trigger when combat damage is dealt.

Skulk matters only as blockers are chosen. Modifying either creature's power after blockers are chosen won't cause the attacking creature to become unblocked.