At the very end of The Hunger Games, during a climatic 2-on-1 battle outside the cornucopia between Katniss and Peeta with a "contestant," a very sick thing happens. Up until now, there were 24 total contestants in the games. When they're killed, a hovercraft appears and drags them into the sky for god knows what. At the very end, you find out "what" they're being used for. Let's just say, if you're a fan of the "gorilla wolf motherfuckers" from Attack The Block then you'll love their distant cousins that show up.
All "21" of them. It's probably the most shocking and violent part of the book, which underscores just how corrupt and evil the capital has been hinted to be. On a scale of the Galactic Empire to Nazi Vampires, this reveal proves the capital may be run by the son of Emperor Palpatine with a Hitler mustache who happens to sound a lot like Montana Max from Hellsing. They're that evil.
It also completely sets up how over their heads Katniss and Peeta are when they think they've fooled the capital.
