A Stock Ball (生命の珠, Ball of Life) is a rare item exclusive to the Subspace Emissary in Super Smash Bros. Brawl, usually appearing after defeating several enemies or completing a puzzle. When picked up, it grants the player one extra life. The extra life's stock icon will show up as the Super Smash Bros. emblem on the lives column on the left side of the screen. This item's prevalence is markedly decreased on harder difficulty settings, to the point that Stock Balls do not appear at all on Very Hard or Intense difficulties, instead being replaced by recovery items.
The Subspace Emissary is played in Stock mode. When you're defeated, your stock decreases by one. If your stock reaches zero, the game ends. However, you can increase your stock by one by picking up a Stock Ball when you come across one. There's a big difference between having a stock of zero and one, so be sure not to leave any Stock Balls behind.