The Lucky Bonus is an extra chest you sometimes see after battle.
The Luffy-player’s Lucky Bonus activated. The player name (censored) is below the item.
The higher your luck stat, the better chances you have of getting the Lucky Bonus chest, which is given to all players in the room, after battle. This is especially useful if you are trying to farm for elusive gold cards from gold chests besides speeding up medals farming.
Update: Lucky Bonus is determined by the luck stat of your main character. The luck stat of your sub character does not matter and you can use whichever character to fight in battle or end the battle with.
Currently, all characters’ luck stat seems to be 3.0%. Press and hold a character you own to see their luck stat. You can raise the luck stat of a character by farming more medals after you reach 6-star, and you get the first +1% with around 32 medals.
The max luck stat is 20% and requires about 630 medals on a 6-star character.
Important: make sure to evolve your 5-star character to 6-start once you hit 180/180. If you waited till 200/180 to evolve into a 6-star, for example, the 20 extra medals do not count towards the 630 medals, i.e. you will end up needing 650 to reach max luck. This has now been patched.
Medals: Max. Luck: Max