The murk of the Wanderbrine concealed unseemly rituals designed to bring out the worst in merrowkind.

Inkfathom Witch

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{2}{U}{B}: Each unblocked creature has base power and toughness 4/1 until end of turn.

New Capenna Commander

Planechase Anthology

Planechase 2012

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{2}{U}{B}: Each unblocked creature becomes 4/1 until end of turn.

Shadowmoor

Fear
{2}{U}{B}: Each unblocked creature becomes 4/1 until end of turn.

An “unblocked creature” is a creature that attacked and wasn't blocked. Creatures aren't “blocked” or “unblocked” until the declare blockers step, so activating this ability before then (or after combat ends) will have no effect.

Creatures stop being unblocked as the combat phase ends. However, they'll stay 4/1 until turn ends.

If Inkfathom Witch is attacking and unblocked, it can make itself 4/1.

Inkfathom Witch doesn't cause creatures to lose their abilities.

The effect from the ability overwrites other effects that set power and/or toughness if and only if those effects existed before the ability resolved. It will not overwrite effects that modify power or toughness (whether from a static ability, counters, or a resolved spell or ability), nor will it overwrite effects that set power and toughness which come into existence after the ability resolves. Effects that switch the creature's power and toughness are always applied after any other power or toughness changing effects, including this one, regardless of the order in which they are created.