He is the Head Gamemaker of the 74th Hunger Games, held by the Capitol. He organizes and leads the Hunger Games under the supervision of President Coriolanus Snow, being in charge of designing the arenas for the games, where tributes of Panem's districts are send to fight to death.
He was portrayed in the live-action film by Wes Bentley, who also played Blackheart in Ghost Rider, Thomas Barclay in P2, Edward Mordrake in American Horror Story: Freak Show and Niander Wallace in Blade Runner: Black Lotus.
In the first book, his name isn't even shown, though it is clear that his influence on the arena is large. In the movie, his role is much bigger; he is interviewed by Caesar Flickerman about his plans for the 74th Hunger Games and his third year into his career as head Gamemaker. He is also present among other Gamemakers in the training center, watching tributes practicing their fighting skills. After three days, all tributes separately show them what they are good in, during the private sessions. When Katniss enters the gym, Gamemakers are too busy by eating and talking to watch her, leading Katniss to shot an arrow directly at their table, skewering an apple in the mouth of a roast pig. This obviously impresses Crane who then give her a 11 training score.
However, he is still cruel and enjoys seeing kids kill each other, as shown that he has a big grin on his face when Katniss is about to die. He is present in the room where Gamemakers control the arena, all the time, but sometimes visits President Coriolanus Snow. During the Games, he comes to Snow for several times to ask him to change rules which would allow two victors, showing a degree of mercy.
Unfortunately, when the last two living tributes, Katniss and Peeta, almost commit a suicide and force Gamemakers to allow two victors, Snow loses his patience with Crane and executes him in the book. In the movie, Crane is locked in the room with a bowl filled with deadly nightlock berries, and he is eventually forced to eat them. His death is a warning of what happens when a person is not completely supportive of the dictator.
Plutarch Heavensbee would go on to take his place as Head Gamemaker, saying in the film that Crane decided to "quit breathing".
In the 75th Hunger Games, Katniss hangs an effigy and paints "SENECA CRANE" with berry juice on its chest. This earned her a 12 training score.