Originally created in 2015, the Lucky Block is a mod for Minecraft which has since gained over 5 million users. The mod adds a new block to the game which, when opened, produces random outcomes. While not all of these are positive, and some are usesless, many contain valuable treasure.
Several special items - a sword, bow, and potion - can occasionally be found in the block. Each of these will produce random outcomes in addition to their standard functions.
The mod aims to make the game more fun by adding an element of randomness and unpredictability. You can even customize all of the outcomes yourself, or download a range of community add-ons.