The free game, developed by Marvelous AQL, was available from the Nintendo 3DS eShop between June 5 and September 30, 2014. It served as a tie-in with the16th Pokémon movie Diancie and the Cocoon of Destruction and has players pit Pokémon collected through StreetPass against thieves from the movie. In fact, StreetPass is the only way to receive two additional starter Pokémon.
Players start by building up their Pokémon army which is made up of Chespin, Fennekin and Froakie. Up to 1000 of each can be in the player's army at a time. The amount of Pokémon the player can take with them into a stage varies from stage to stage.
Winning conditions of a battle are based on both the number of units and the Pokémon type of the unit. Pitting the right type against the right opponent is key. The concept is very similar to the rock-paper-scissors battle system found in the StreetPass Mii Plaza game, Warrior's Way a.k.a. StreetPass Battle.
Stages are split into several sections and the player can choose to leave the current army behind in their current spot to regroup and gather additional troops before rejoining with the veterans and continuing through the game.
Players can spend 5, 10 or 15 Play Coins to receive a variying amount of Pokémon in return, the amount of which changes depending on the game progress.