Unimpeded Trespasser

Uninvited Geist

Skulk (This creature can't be blocked by creatures with greater power.)
When Uninvited Geist deals combat damage to a player, transform it.

Uninvited Geist // Unimpeded Trespasser

Fogwalker

Skulk (This creature can't be blocked by creatures with greater power.)
When Fogwalker enters, target creature an opponent controls doesn't untap during its controller's next untap step.

Skeleton Key

Equipped creature has skulk. (It can't be blocked by creatures with greater power.)
Whenever equipped creature deals combat damage to a player, you may draw a card. If you do, discard a card.
Equip {2}

Behind the Scenes

Creatures you control have skulk. (They can't be blocked by creatures with greater power.)
{4}{W}: Creatures you control get +1/+1 until end of turn.