The Dual Set-Up System, abbreviated DSS in the game, is a gameplay mechanic introduced in Castlevania: Circle of the Moon. The game's protagonist, Nathan Graves, can collect magical cards and combine their effects for a variety of magical abilities, from changing his whip into different weapons, to summoning creatures to attack.
To create a DSS effect, Nathan must possess at least one Action Card and one Attribute Card, and select one of each type in the DSS menu. At first, the description of a specific card combination is still unknown (indicated by "???"). The player needs to activate them in-game in order for the description to be displayed, along with the corresponding stat bonuses. These cards are dropped from specific enemies, and once obtained, are never lost or used up. DSS effects consume MP, some by each use of the skill and some by the amount of time the skill is deployed.
Action Cards
Action Cards allow Nathan to perform new abilities and are represented by Roman Gods.