Trying your luck and rolling for your favorite characters is one of the best activities to do in Zenless Zone Zero. But you'll need a fair amount of Master Tapes to fund your ventures.
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Master Tapes and Encrypted Master Tapes are a form of currency that you need so that you can roll for different characters in different banners. It is the main way that players can build up their character roster, allowing them to create different team compositions to decimate their enemies in the story, in different committees, and beyond.
If you want to get more characters, you can read here how to get and use Master Tapes in ZZZ.
To obtain Master Tapes and Encrypted Master Tapes in ZZZ, you will need to purchase them from the Signal Shop using Polychrome. Polychrome can be found in a variety of ways, including purchasing them with real money, completing various quests, and more.