Within each set, there are expansions, which often introduce new characters, gameplay tweaks, or card artwork
This is where you can buy a plethora of different items using either coins - the free currency earned by winning matches, completing daily quests and levelling up your Mastery Pass - or gems, which are mostly purchased with real money
Before you even think about the cards inside, start with the packaging
In particular, this doesn't cause the final chapter ability to trigger again
Otherwise, reveal your entire hand, then place it on the top of the Deck in any order
Since EDH lets you play any Magic: The Gathering card from any MTG set (if it's not on the Commander banlist), there are a lot of extremely scarce, extremely powerful cards in this format, and players are looking to Commander Masters to deliver some choice reprints and drive those prices down