Like the shop donation machine from Rebirth, reaching donation milestones unlocks new items and game features for future runs. When Ultra Greed is defeated, a donation machine appears. On each floor, facing waves of enemies rewards the player with money, which can be used to buy upgrades. The new game mode in the Afterbirth expansion, Greed Mode, is a seven-floor challenge with a boss fight against Ultra Greed at the end. The final reward (The Keeper) was not patched into the game until the community solved the puzzle, and many puzzle elements were not in the game at all, requiring Twitter, voice mail, and even two real-world expeditions to solve. With the release of the Afterbirth expansion in October 2015, there was a new secret, but this one was not so easily datamined. However, dataminers quickly discovered his existence by looking at the game code and The Lost became common knowledge in a few days, much to the disappointment of the game creators. When The Binding of Isaac: Rebirth was released in November 2014, a super-secret character called The Lost was included, with a complex unlocking mechanism that was designed to be a community scavenger hunt - an ARG of its own.