Uninvited Geist
Creature — Spirit
Skulk (This creature can't be blocked by creatures with greater power.)
When this creature deals combat damage to a player, transform it.
A slow knock at midnight is best left unanswered.
Unimpeded Trespasser
.
Creature — SpiritThis creature can't be blocked.
Knocking was simply a formality.
Dan Murayama Scott
Rulings
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.
(wotc • 2016-04-08)
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.
(wotc • 2016-04-08)
Rulings
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.
(wotc • 2016-04-08)
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.
(wotc • 2016-04-08)