

R2API.Unlockable is a submodule assembly for R2API that allows mod creators to add new Unlockables and Achievements to the game. These can later be used to gate certain content pieces from your mods so that an achievement needs to be unlocked before you can get to use a specific content (such as an item)
R2API.Unlockable is mainly used for adding Unlockables that get unlocked after obtaining an AchievementDef, please note that unlocks such as stage / monsters log books should not be added with R2API.Unlockable but rather with R2API.ContentAddition
A valid unlockable and achievement pair is defined by a class that inherits from both BaseAchievement and IModdedUnlockableDataProvider, which gives enough data to create both the UnlockableDef and AchievementDef.