Posi, Lord of the Depths

When Posi, Lord of the Depths enters the battlefield Pursuit 4 (reveal the top 4 cards of your library, choose a permanent from those with cmc equal to or less than the cmc of the card Persuiting)
{4}: creatures you cast this turn gain "when this creature enters the battlefield Pursuit 4"
{t}: mill 3 then, shuffle 2 cards from your graveyard into your library