There were lots of factors leading to Covenant's action that night.
But the author tells us what was the first and foremost factor.
It wasn't about being in a dream. Believing you are in a dream and acting freely on your inclinations is a freedom, and a freedom makes you happy.
In [i]Lord Foul's Bane[/i] was written wrote:Covenant felt suddenly trapped, threatened. A pressure of darkness cramped his lungs; he could not seem to get enough air. A leper's claustrophobia was on him, a leper's fear of crowds, of unpredictable behavior. Berek! he panted with mordant intensity. These people wanted him to be a hero. With a stiff jerk of repudiation, he swung away from the gathering, went stalking in high dudgeon between the houses as if the Stonedownors had dealt him a mortal insult.
Berek! His chest heaved at the thought. Wild magic! It was ridiculous. Did not these people know he was a leper? Nothing could be less possible for him than the kind of heroism they saw in Berek Halfhand.
But Lord Foul had said, He intends you to be my final foe. He chose you to destroy me.
In stark dismay, he glimpsed the end toward which the path of the dream might be leading him; he saw himself drawn ineluctably into a confrontation with the Despiser.
He was trapped. Of course he could not play the hero in some dream war. He could not forget himself that much; forgetfulness was suicide. Yet he could not escape this dream without passing through it, could not return to reality without awakening. He knew what would happen to him if he stood still and tried to stay sane. Already, only this far from the lights of the gathering, he felt dark night beating toward him, circling on broad wings out of the sky at his head.
He lurched to a halt, stumbled to lean against a wall, caught his forehead in his hands.
I can't - he panted. All his hopes that this Land might conjure away his impotence, heal his sore heart somehow, fell into ashes.
Can't go on.
Can't stop.
What's happening to me?
This is a man having a breakdown. He is suffering from traumatic stress. He feels like he's going crazy, dark batwings of pressure and fear surround him, keep him from thinking clearly.
Faced with trauma, people tend to respond in one of four ways: fight, flight, freeze, or faun.
"Are you married?"
At that, he whirled to face her as if she had stabbed him in the back. Under the hot distress of his eyes and his bared teeth, she faltered, lowered her eyes and turned her head away. Seeing her uncertainty, he felt that his face had betrayed him again. He had not willed the snarling contortion of his features. He wanted to contain himself, not give way like this. not in front of her. Yet she aggravated his distress more than anything else he had encountered.
In the night, Lena tries to comfort him. But she does not understand Covenant's complex problems. Her actions, instead, provoke him. She keeps trying to help him, and he keeps being provoked - she's pushing the wrong buttons.
Until, finally, finally breaks.
Covenant's back clenched abruptly still, and he said with preternatural quietness, "Are you trying to drive me crazy?"
His ominous tone startled her, chilled her. For an instant, her courage stumbled; she felt the river and the ravine closing around her like the jaws of a trap. Then Covenant whirled and struck her a stinging slap across the face.
Covenant chose fight.
It wasn't about being in a dream. Nothing was indulged - nothing about his assault on Lena was about sexual pleasure.
Covenant doesn't think it's a dream - he thinks it's a nightmare. It is a complex and perfectly tailored form of torment. He cannot figure a way out, and he can see quite vividly that not getting out will be fatal to him.
This is an existential crisis for him.
The fight response to traumatic stress is to attack the cause of your pain. That's what Covenant is doing, in so far as Lena is the present embodiment of his torment.
Are you trying to drive me crazy? Attacking the cause of your pain isn't logical, isn't practical in any sense, it is a primal instinctual response. Make it go away.
Only after he has struck Lena does Covenant begin to consider rape. His passions are awoken, and he is not yet able to control his regenerated libido. And Rape is about power, not lust - unthinkingly, he is trying to achieve some sort of power from among his many helplessnesses. His passion and his anger are easily diverted from one form of assault to another.
He may indeed feel a license from being in a dream, but the author does not say so AFAICT.
The more astute observation is that Covenant, having been helpless and impotent, lacks any kind of restraint or self-awareness when an opportunity for power presents itself.
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