Callistus III is elected pope. Born into the infamous Borgia family, Pope Callistus III will name one of his nephews cardinal and he in turn will become Pope Alexander VI.
Callistus III is only elected to the papacy, though, because he's so old and feeble that the other cardinals think he's a safe compromise. They're right: he never does much and spends most of his reign as pope in bed, sick.
The only notable thing which Pope Callistus III does is call for a Crusade against the Turks who had take Constantinople two years ago. This, however, didn't amount to anything anyway because none of the Christian rulers in Europe are interested in participating in a Crusade.