As soon as you step on the drawbridge, a giant Troll
will appear. Go back a few steps and pick up the spear. Throw
it at the Troll and it will die instantly.
Use the following trick to defeat the Troll at the top of the
walkway. When you run up the ladder, do not go up all the way
on the platform with the Troll. Stand behind the small wall and
use a ranged attack. The Troll cannot reach you, though he will
swing at you. The Orcs and other enemies cannot get past him and
also cannot hurt you. It takes a few shot to bring down the Troll,
but you will not be injured.