Double cards are cards that are connected to each other as long as they are in your deck or during mulligan. If you draw them or if they leave your deck due to any other effect, they will split into their two component cards. After the split, they are considered two different cards and any effect targeting one of them will not affect the other (using a Soul Tear on a Baliwog will only return Baliwog to your hand and not Spawn Mother). The following rules are used for double cards:
- Drawing a double card only counts as a single card drawn, for effects like Arcanaeum Librarian and Abandoned Imperfect.
- When you have 9 cards in your hand and draw a double, it will split and leave you with 11 cards in hand.
- Double cards can't be created by random generation effects (for example, Wabbajack can't transform a creature into a double card or a component of a double card).
- Buffs to double cards are applied to the double, and when it splits the buff is applied to both components. For example, drawing a double card with Eclipse Baroness will reduce the cost of both component cards by 2, and Ancestor's Battleaxe will result in both Baliwog and Spawn Mother getting +4/+4.
- Double cards pre-split have the combined types, attributes, names, costs, power, and health of the two component cards. Any effects which look for cards in deck with specific properties will see the combined properties of the composite cards. Things get weird when dealing with combined card types, and differ based on the type of effect:
- Buff in deck (Ancestor's Battleaxe, Caius' Machinations): these effects hit double cards where either component is the appropriate type.
- Draw from deck (Sun-in-Shadow, Apex Wolf): these effects hit double cards where either component is the appropriate type.
- Summon creature from deck (Altar of Despair, Sails-Through-Storms): these effects hit double cards where both components are creatures. For example, an Altar summoning a 6-cost creature can summon a Baliwog and Spawn Mother from your deck, but an Altar summoning a 4-cost creature will not be able to summon a Baliwog Tidecrawlers (because Smoked Baliwog Leg is an action).
- Other (Mecinar, Siege of Stros M'Kai): double cards are skipped over.