Duel Decks are a series of theme decks that started in 2007 with Elves vs Goblins. They contain two 60-card decks designed and developed specifically to be played against each other by two people. Cards appearing in these sets may be from any non-Un set in Magic history but are in the post 8th edition card frame, with a black border. Each set has its own expansion symbol. The first in the series, Duel Decks: Elves vs. Goblins, contained eight rares, including two foil rares with alternate art. Later sets in the series changed this this to two foil mythic rares with alternate artwork, and between six and ten rares, as well as four non-foil cards with alternate artwork (except for Divine vs. Demonic, which had five). Many of the mythic rares were originally printed as rares, and have been changed mythic status for the duel deck. Some of the cards also have new flavor text.
Each set depicts a notable rivalry. Until Venser vs. Koth, the sets alternated between showing two rival factions, and two rival planeswalkers, and often tie into current or future storylines. For example, Elves vs. Goblins was released during the tribal block of Lorwyn; Jace vs. Chandra tied into the webcomic Fuel for the Fire; and Phyrexia vs. the Coalition, Elspeth vs. Tezzeret, and Venser vs. Koth tie into the Scars of Mirrodin block.