how to use side deck yugioh | Yu-Gi-Oh! Wiki Side Deck. : r/yugioh

It seems possible

For example, Exodia decks with mostly Normal Monsters can use Heart of the Underdog to extend your Draw Phase, increasing the chance of drawing Forbidden One cards

Tapu Koko-GX 135/145 - Guardians Rising Holofoil Tapu Koko-GX 135/145 - Guardians Rising Holofoil The Pokmon Company When you play this Pokmon from your hand onto your Bench during your turn, you may move any number of Lightning Energy from your other Pokmon to this Pokmon

Once per turn: You can target 1 face-up card on each player's field, except this card

Similarly, The Aetherspark also routinely sells for over $1500

What's important is that the card is still legal for tournament play because it cannot be distinguished from other cards in the deck when sleeved