To set up play, lay out 25 word cards in a 5×5 grid. Place a key card in the holder so that each player sees one side of the card. Each player sees a 5×5 grid on the card, with nine of the squares colored green (representing Members) and three squares colored black (representing Death Eaters). Three of the nine squares on each side are also green on the other side, one Death Eater is black on both sides, one is green on the other side and the other is an innocent bystander on the other side.

Collectively, you need to reveal all fifteen Members — without revealing a Death Eater — before time runs out in order to win the game. Either player can decide to give the first one-word clue to the other player, along with a number. Whoever receives the clue places a finger on a card to identify that Member. If correct, they can attempt to identify another one. If they identify a bystander, then their guessing time ends. If they identify a Death Eater, you both lose! Unlike regular Codenames, they can keep guessing as long as they keep identifying a Member each time; this is useful for going back to previous clues and finding ones they missed earlier. After the first clue is given, players alternate giving clues.

The cards that players need to guess feature a word or phrase on one side and an image on the other.