The soft creak of trees in the wind is not always cause for comfort.

Ancient Lumberknot

Each creature you control with toughness greater than its power assigns combat damage equal to its toughness rather than its power.

The List

Innistrad: Double Feature

Innistrad: Crimson Vow

Ancient Lumberknot's ability doesn't actually change any creature's power. It changes only the amount of combat damage the creature assigns. All other rules and effects that check power or toughness use the real values, even if they cause damage “equal to a creature's power” to be dealt.