Primitive

In the distant future,
 scientists are conducting an experiment with time in a laboratory
 in the United States. Using their technology, they teleport a primitive man from a parallel universe.
 A malfunction and explosion occur in the room where the experiment was taking place... Something went wrong...
 The capsule containing the man was opened—he emerges and picks up his battered wooden club, which had fallen 
in the explosion. Everyone else in the room perished... The player, overcome with rage and madness at the realization that he understands nothing, 
picks up the club and runs to kill everyone who gets in his way. 
Theme: A primitive man from the past. Restriction: He is evil, he kills everyone.