They are a product that contains approximately 10 cards, but can sometimes have different amounts depending on the set, or region around the world
Echo of Eons pulls double duty: You get two wheels if you cast it naturally, but it pairs nicely with any discard wheels since you can flash it back later
Played (PL) A Played card looks as bad as you can get a card through regular use without sleeves
They were identified as problems to the casual aspect of Commander, as they tend to deny players resources, drastically change the rules, or otherwise create a feels bad moment during the game
The super rare and secret rare Digimon cards are worth hundreds of dollars
However, it is clear that by using the extra card, a player can gain extra resolution in their land-drop frequencies, allowing more fine-tuning for mana ratios