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Madness cannot destroy itself but can destroy other copies of Madness. If there are both eternal and non-eternal Jokers present Madness will always destroy a non-eternal Joker.

As of update 1.0.1f-full there are 150 total jokers of varying rarities with 105 unlocked from the start and 45 unlockable through specific conditions.

To download directly from the operator there are links on the site leading to download pages so you can use these to make things simpler and ensure you are getting the right app.