The main members of the archetype act as mirrors of each other. They generally represent the duality of dreams and nightmares. Many of the Monsters of this set are named after the Greco-Roman gods of sleep and dreams, which explains the archetype’s mechanic of switching between the field spells “Dream Mirror of Joy” and “Dream Mirror of Terror”, a thematic representation of switching from dreams to nightmares.
“Ikelos, the Dream Mirror Sprite” and “Ikelos, the Dream Mirror Mara” are named after the god Ikelos, whom was considered benevolent among the gods, but could be a terror to mankind when he brought them bad dreams. “Morpheus, the Dream Mirror White Knight” and “Morpheus, the Dream Mirror Black Knight” are named for Ikelos's more famous brother, Morpheus.
Phantasos, the brother of Morpheus and Ikelos, is the god of fantasy and illusions, a defining quality of dreams and nightmares. "Phantasos, the Dream Mirror Friend" and "Phantasos, the Dream Mirror Foe" are named after him.
Finally, "Oneiros, the Dream Mirror Erlking" takes its name from two mythological entities: the first being the personification of Dreams Themselves (oneiros/oneiroi), and the second being the Erlkonig or Erlking, a malevolent, Germanic forest spirit that was said to steal the souls of children. Oneiroi could also be used to refer to all three of the aforementioned dream gods (Morpheus, Ikelos and Phantasos).
"Dream Mirrors" focus over both their respective Field Spells, "Dream Mirror of Joy", and "Dream Mirror of Terror" to summon the Counterparts of the Main Deck, "Dream Mirror" monsters by tributing, locking down the opponent, and punishing the opponent if they Special Summon a monster(s). The DARK "Dream Mirrors" monsters focus over disrupting the opponent's strategies by destroying their cards, lowering their ATK, allowing direct attacks while the LIGHT "Dream Mirror" monsters focuses on protection, searching, and adding key cards to the hand. Their Spells and Traps also depend on which Field Spell is on the field from banishing cards to having an advantage.
The primary strategy of "Dream Mirrors" is to resolve the effect of the trap card "Dream Mirror Hypnagogia" to activate both of their field spells. This allows the DARK and LIGHT monsters to activate their effects to tribute themselves to special summon their counterparts in the same turn and also gives their Spell and Trap cards more versatility to activate their effects. This greatly increases the deck's speed and ability to control as long as the player can maintain both field spells. "Dream Mirror Hypnagogia" combos well with cards like "Field Barrier" and "Set Rotation", as its effect to place Field Spells (instead of activating them) means that these cards can disrupt the opponent's ability to remove the "Dream Mirror" Field Spells while giving the "Dream Mirror" player freedom to set their field spells as needed.