Playing with Sonar MonstersEdit
A Sonar Summon is conduced when a face-up Sonar Monster has a number of Sonar Counters equal to its level. In order to Sonar Summon a monster, the player must flip it face up on his extra deck first. The player can flip up to 2 at a time, but there is no limit of how many Sonar Monsters can exist face up in the Extra Deck, considering the Sonar Pendulum Monsters. The most common way of gaining Sonar Counters is by the own effect of the Sonar Monsters flipped face up in the Extra Deck, but there are many supporting cards that will also generate Sonar Counters. So, just like Pendulum monsters, the Sonar monsters can exist face up in the Extra Deck.