Ruga, Chaos Dungeon Master

Must activate the ability in sequence:
-When this card enters the battlefield you may pay:
-{p/u}: you become the dungeon master:
-{p/u}: your opponent can only cast two monsters
per turn:
{dash}{p/g}: you gain one poison counter at each of your
upkeep phase rounded up:
When you pay x for the mana cost that is its
power and toughness.