If you're building a sideboard and have no idea what the meta will bring, you'll want to use generally good, versatile cards that cover many bases and sure up your own deck's weaknesses instead of trying to guess exactly what you'll come up against
Add the dynamic duo of Crimson Haze Scarlet & Violet to your squad and dominate the Japanese Pokmon TCG
The Witch-King Rides to War The Lord of the Rings: Tales of Middle-earth Scene Box Flight of the Witch-King Universes Beyond: The Lord of the Rings: Tales of Middle-earth I love a good villain and Saurons lieutenant, The Witch-King, is one of my favorites in all of literature
Serious about protecting your cards
Maestros Ascendancy is the Kess we have at home, but none the worse for it
While the card has become a sideboard staple of green decks throughout Modern, it has funnily enough made the most impact in Vintage, where its a great card against all the artifact decks while also providing Bazaar of Baghdad decks a reliable answer to Grafdiggers Cage and Leyline of the Void without requiring mana