Would Pot of Extravagance be too unfair if you use a deck that doesn't use an Extra Deck?
If you use one of these types of decks, could you just put "useless" cards in your Extra Deck that you don't plan on using so there is no cost to using Pot of Extravagance?


Yes you can.

You can build your deck and extra deck the way you want, as long as you stick to the current Banlist (on an official game, that is) and the game rules.