What character are you introduced to in the first paragraph? What is he looking for in the forest?

That would be Ulrich von Gradwitz. He patrolled the dark forest in quest of a human enemy (Georg Znaeym).

Ulrich von Gradwitz is the character introduced in the first paragraph. He is described as standing outside on a winter night, watching and listening with his rifle as though he is hunting. However, he is looking for a human enemy.