A motif is a repeated idea in a story. In this story, motifs are savagery and darkness.
In “The Most Dangerous Game,” Connell carefully weaves a story of betrayal and savagery. General Zaroff’s system is a betrayal of civilization and humanity. People just do not use each other for sport. It’s against the social contract. He also betrays Rainsford by forcing him to play the game. Rainsford in turn betrays him symbolically by killing him instead of playing the game on the general’s terms.
The entire story pretty much takes place at night, so darkness is a literal concept. However, the actions of the men are also dark. General Zaroff has a dark soul. Rainsford has to find the darkness in himself in order to survive.