Cluster is the identity of a card that differs its characteristic from other cards. It's similar to colors in Magic: the Gathering. There are currently five clusters available in Dreadnought (the fifth one, green, was introduced later in Chapter 5) not including the cluster ALL.
List of ClustersEdit
The clusters of your casters are important since they determine which card is permitted to be put into your deck. Each unit and code card has a deck construction condition at the top right section. If the cluster symbols shown there match the cluster symbols that you casters have, you may put that card in your deck. The example is presented below.