Also known as "The Great Naga," Bolshie was spawned from Marty's farewell letter and has a tenuous relationship with Valor, both helping and trying to kill him on multiple occasions. Valor first meets Bolshie when he is chased by him through the Southern Pit, and when Valor finds Marty in the Mechanical Mine, Bolshie is there once again to protect Marty. Later in the game, however, Bolshie assists Valor by granting him access to The Tunnels and the Red Plains.
Bolshie can be found at each fast travel point in the game, where he will partially emerge from a tunnel when you get close. Hitting him will make him retreat back into the tunnel, but this does not affect whether or not he is hostile later on.