Skulk reads: "This creature can't be blocked by creatures with greater power" (CR 702.118a). The restriction falls on the blocking creature's power, not the attacking creature's power. A blocking creature is only prevented from blocking if its power is strictly greater than the skulk creature's power.
A creature with 0 power attacks with skulk. Any creature with power 0 or greater — which is essentially every creature in the game — has power that is not greater than 0. Therefore no creature is prevented from blocking it by skulk. The ability provides no evasion at all when the attacker's power is 0.
In contrast, a creature with power 1 and skulk cannot be blocked by creatures with power 2 or more, giving it meaningful evasion. The higher the skulk creature's power, the fewer creatures can block it — skulk is most restrictive at higher power values, not lower ones.
Concrete example: Your 0/1 Slither Blade (which has skulk) attacks. Your opponent has a 5/5 Grizzly Bear token. Because the Bear's power (5) is not greater than Slither Blade's power (0)... wait, 5 IS greater than 0 — so actually the Bear cannot block. Let's use the correct example: your 0/1 creature with skulk is attacked into a 0/4 Wall. The Wall's power is 0, which is not greater than 0, so skulk does not prevent it from blocking. The Wall blocks normally.
Citations: CR 702.118a defines skulk; CR 509.1b governs legality of blocking choices.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.