What is Simon's function in the novel? And how does he die?

Simon is seen by many as a Christ-like figure.  He has an
ability to work between the two groups without any real problem and he is particularly
careful to look out for the little kids in the group.  He also has a strange intuition
and an ability to in a certain way predict things about the future.  The boys think him
strange but give him a certain respect.

As the novel
progresses, he wanders off into the woods and sees "the beast" after a vision in which
the pig head on a stick talks to him.  He is the only boy who understands that the beast
is the fear inside the boys.

It is just after this vision
that he stumbles out of the woods in the midst of one of the games of the boys where
they play-kill a pig and in their moment of fear and blood lust they fall on Simon and
kill him.