Mournwillow

Haste
Delirium — When this creature enters, if there are four or more card types among cards in your graveyard, creatures with power 2 or less can't block this turn.

Shadows over Innistrad Remastered

Haste
Delirium — When Mournwillow enters the battlefield, if there are four or more card types among cards in your graveyard, creatures with power 2 or less can't block this turn.

Eldritch Moon

Because the last ability’s effect doesn’t change the characteristics of any permanents, the set of creatures affected is constantly updated. Any creature with power 2 or less at the moment blockers are chosen will be unable to block.