In battle, in forest, at the precipice in the mountains,
On the dark great sea, in the midst of javelins and arrows,
In sleep, in confusion, in the depths of shame,
The good deeds a man has done before defend him.
"Mørk" is the adjective, so that wouldn't work. You could use "et mørke", but this is one of those cases where Norwegian prefers the definite form of an abstract noun.