Urborg Lhurgoyf

You may kick Urborg Lhurgoyf only once for its {U} cost and only once for its {B} cost. You can kick it twice by paying {U}{B}, but you can't kick it twice by paying {U}{U} or {B}{B}. You can't kick it more than twice.

Urborg Lhurgoyf's second ability isn't a triggered ability and doesn't use the stack. Players can't cast spells or take other actions after it enters the battlefield but before its controller mills cards.

If it was kicked, Urborg Lhurgoyf enters the battlefield with a power and toughness determined by the number of creature cards in your graveyard after you have milled cards for each time it was kicked. For example, if you have one creature card in your graveyard before it enters the battlefield and you mill two more creature cards with its ability, it enters the battlefield as a 3/4 creature.