Disenchant, Negate, and Duress are examples of cards seemingly tailor-made for the sideboard, and too narrow for the main
This is not as impressive, but with Moonlit Hill, you can attach an Energy to several of your Pokmon, then heal the damage put on all of these Pokmon
You can also swap Dross Scorpion out for Staff of Domination if the sacrificed creature has 8+mv, such as Shadow of Mortality
After making a copy of the Twelfth Doctor I cast Twice Upon a Time with two demonstrate effects so I was ready to take some extra turns, and so would my opponent if they lived after my turns
Aadimos un poco de Gacha a tu Carrito?
If your adversary has been loading up, for something like a Pikachu & Zekrom GX that uses six Energy, you could take a swing that makes them regret it