Pressure Monsters, colored Ruby, exist in the extra deck an are cards representing a combination of one or more monsters and a Pressure Spell cards or Pressure Trap cards. Pressure Monsters like Synchro, fusion, and exceed monsters may only be included in the extra Deck, and cannot exist in the hand or Main Deck. If a Fusion Monster is returned to its owner's hand or Deck, it is instead sent back to the Fusion Deck. However, they may be sent to the Graveyard when destroyed, as well as Removed from Play.
in order to Pressure summon a Pressure monster you must send from your side of the field a monster card or cards and a Pressure Spell card/Pressure Trap card listed in its Pressure Materials. this summoning is similar to Hybrid summoning and Synchro summoning