Whenever a permanent with ward becomes the target of a spell or ability an opponent controls, counter that spell or ability unless that opponent pays whatever cost is after the word "ward." That cost can be mana, life, or pretty much anything else that can be a cost
Previously, in cases where a card's mana value differed from the resulting spell, such as with some modal double-faced cards or cards with an Adventure, you could cast a spell with a higher mana value than the exiled card
The Shapeshifter subtype does not have anything particular about it
Try mixing in Jumpstart Boosters from other sets like March of the Machine or Jumpstart 2022 to brew up new deck synergies, because Jumpstart Boosters are compatible with each other regardless of the set they're from
Ashiok, Nightmare Weaver can do three at a time, Ulamog, the Ceaseless Hunger can exile 20 cards at once and Ulamog, the Defiler exiles the top half of an opponent's library