Depends on the timeframe, I guess. During the golden age, Massassi would most likely be on guard alongside Tu'kata and other Sith abominations. Non-Force sensitives would be slaughtered quickly. During Exar Kun's time, when Korriban was abandoned, the undead and the beasts would be the danger. During the Great and Cold Wars... Imperial troops would shoot them down. I like to think that if ultimately you didn't die by the beasts and other dangers, the Sith spirits would drive you insane. You'd be lost there forever and eventually die, probably from suicide or starvation.