I've found some fascinating accounts of the story about the fallen angels and the giants--apart from the Book of Enoch. This is important to me, as the origins of the Wolf King begin in our world before The Flood, and because these agents of the ancient world continue in his realm.
The Voyage of Saint Brendan
At that, one of the birds flew off the tree, and as he flew his wings had a tinkling sound like little bells. He flew over to the boat where the saint was seated, and, perching on the prow, he spread out his wings to show how glad he was to meet Brendan.
Then the saint, realizing that his prayer had been granted, said to the bird, "if you are a messenger from God, tell me where all these birds come from, and why they are gathered together here."
The bird answered, "We are the victims of the ancient enemy. Through no fault of our own, we fell from heaven with Lucifer and his followers. But God, who always dispenses justice, sent us to this place, where we suffer no pain, and where we can see a little of the divine presence. But we must be kept apart from the angels who remained faithful to God.
"We wander the world, in the air, and earth, and sky, like the other spirits on their missions; but on festival days we take the shapes you see, and come here, and sing the praises of our Creator."
From the Testament of Solomon
And there came before my face another enslaved spirit, having obscurely the form of a man, with gleaming eyes, and bearing in his hand a blade. And I asked: "Who art thou?" But he answered: "I am a lascivious spirit, engendered of a giant man who died in the massacre in the time of the giants." I said to him: "Tell me what thou art employed upon earth, and where thou hast thy dwelling."
And he said: "My dwelling is in fruitful places, but my procedure is this. I seat myself beside the men who pass along among the tombs, and in untimely season I assume the form of the dead; and if I catch any one, I at once destroy him with my sword. But if I cannot destroy him, I cause him to be possessed with a demon, and to devour his own lesh, and the hair to fall off his chin." But I said to him: "Do thou then be in fear of the God of heaven and of earth, and tell me by what angel thou art frustrated." And he answered: "He destroys me who is to become Savior, a man whose number, if any one shall write it on his forehead, he will defeat me, and in fear I shall quickly retreat. And, indeed, if any one write this sign on him, I shall be in fear." And I Solomon, on hearing this, and having glorified the Lord God, shut up this demon like the rest.