 Specifically, Ken Shamrock has been a longtime rival of Royce Gracie, and Frank Shamrock has engaged in a feud with the Cesar Gracie camp.The Lions Den was one of the camps who participated in the late International Fight League.Coached by MMA legend Ken Shamrock, the Lion's Den took the place of the Nevada Lions when the IFL decided to focus more on a camp-based system than a team-based system.