Riddle Me This

Contest Entry

MY FIRST IS IN GIGGLE AND ALSO IN LAUGH,
MY SECOND IS IN THIRD AND IS ALSO IN HALF
MY THIRD IS IN HORROR AND ALSO IN BONE.
MY FOURTH IS IN SUN BUT NEVER IN MOON,
MY FIFTH IS IN CASTLE AND ALSO IN KNIGHT,
MY WHOLE WALKS THROUGH WALLS TO GIVE PEOPLE A FRIGHT.

Do you know who I am?

-Word count: Maximum 500.