Shaco
Most would say that death isn't funny. It isn't, unless you're Shaco - then it's hysterical. He is Valoran's first fully functioning homicidal comic; he jests until someone dies, and then he laughs. The figure that has come to be known as the Demon Jester is an enigma. No one fully agrees from whence he came, and Shaco never offers any details on his own. A popular belief is that Shaco is not of Runeterra - that he is a thing from a dark and twisted world.
Excerpt from the official biography by Riot Games — Universe of League of Legends. Story and characters © Riot Games.
View the original biography at Riot Games — Universe of League of Legends