Fixed Rarity cards are cards issued in Starter Decks, Structure Decks and some Speical Sets whose Rarity doesn't affect whether you get the card or not: You are gauranteed to get the card. As for the gauranteed gain, the card, if sold individually, usually yields less price compared a card from Booster Pack of the same rarity. Usually, Fixied Rarity are at most Ultra Rare or Super Rare. One such example of a Fixed Rarity card is "Red-Eyes Darkness Dragon", which was printed as an Ultra Rare in every edition of Structure Deck: Dragon's Roar.