Secret Crystal Cave

The Secret Crystal Cave was a special Event first introduced in the Wicked Breakout Party update, as part of the first anniversary celebrations for Cookie Run: OvenBreak. It is a special area that can only be accessed by collecting "CRYSTAL" letters that are found throughout all game modes whenever the Cookie is running.

Upon collecting the CRYSTAL letters, the player can then select any Cookie or Pet they'd like to choose to traverse the Crystal cave, though there are special occasions where equipping a certain Combi would grant the Cookie a small magnet, such as with equipping and $π$. However, there's a caveat that the cave can only be entered once a day.

When entering the cave, the Cookie is first seen running in an area similar to the Yeti's Frozen Cave from the Escape from the Oven Breakout Episode, before then transporting into a special Bonus Time that is filled to the brim with Crystals, where collecting one small crystal gives one Crystal in-game, and giant flying crystals, which give 20 Crystals each. The cave then ends with an exit similar to ones found in the Island of Memories.

Currently, the cave has only appeared twice, with dates of appearance being relatively close to each other, before it's seemingly permanent retirement. It's unclear why the cave has been retired, though it could be due to the nature of collecting Crystals in the current state of the game, alongside the introduction of the reoccurring special Event, Curious Rainbow Mine.

Trivia

 * The Secret Crystal Cave has two themes exclusively tied to it. Neither of the themes have made any appearances in-game after the cave's retirement. Though the Bonus Time theme has appeared on occasion regarding the promotional material of Cookie Run: OvenBreak.