After their first duel, and between each duel from then on, each player can choose to replace cards in their Main Deck and/or Extra Deck with cards from their Side Deck
They are typically great cards and they partly occupy a similar portion of the cube to removal but you do want a mix
Destiny HERO - Plasma X DARK Level 8 [ Warrior / Effect ] ATK 1900 DEF 600 Cannot be Normal Summoned/Set
While having each deck correspond to a single game is thematically tight, it doesnt make the best use of each Commanders strengths
If you do, this card's Level becomes the revealed monster's Rank, also while it is face-up in the Monster Zone, you cannot Special Summon monsters from the Extra Deck, except "Number" Xyz Monsters
When a popular collectible sells for big bucks like the 1998 Pokmon Illustrator (unnumbered Trainer trading card) trading card that sold for a record $375,000 in 2021, people take notice