Stealing something like an opponents commander or combo piece can absolutely shut down their game plan, though you have to be careful since it is an aggressively unfun strategy
Common Uncommon Rare Super Rare Legendary Enchanted Take a look at the symbol at the bottom of these three character cards from The First Chapter
9.8 A purchased Lot shall be at the Buyer's risk in all respects from the fall of the Auctioneer's hammer whether or not payment has been made and neither the Company nor the Seller shall thereafter be liable for, and the Buyer indemnifies the Company against, any loss or damage of any kind, except where the Company (and its employees or agents) has not acted with due care and skill
But it goes furtherif you cast it from exile, with or without using foretell, you also prevent all damage that would hit you for the turn
Can I use cards from any Disney set in my deck
Casting a legendary spell from your hand lets you exile cards from the top of your deck until you find another legendary nonland card that costs less than your initial spell