"I love you" is the balm after the whip, the lewd purr in his ear, the reward for decapitating a slave whose only crime was saying no. It is the sound of wandering hands and the splash of wine in a chalice and the hissing scream of blood magic contorting a dead elf child's body. "I love you" means he is nothing without the love of his master; it is control, degradation, taking without consent or warning.
He tenses and looks away when Hawke says them, when Hawke murmurs them into his skin.
"I—I'm so sorry," the mage (yes, mage, a manipulator of reality, just like Danarius, just like-) "Am I going too fast for you?"
How can he explain? He hesitates. He does not want to talk about it. He does not want Hawke to know how vulnerable he is, because then Hawke might leave him and that is worse than Hawke hurting him.
"It's not that," he says quietly. "It has a different meaning for me than it does for you. I…care for you, as well."
Confusion, and then comprehension, dawn on the mage's features. He gives a shaky little breath, and then pulls Fenris to him, warm and strong and yet ever so gentle.
"I see," Hawke says. He ponders for a moment. "I will have to get creative then. Let me think. What could I say to you, love, to express the depth of my devotion?" His voice is airy and cheery, and Fenris cannot help but smile slightly, secretly liking it when Hawke is light enough for the both of them.
"How about this, then," Hawke says, taking his face in his hands and looking at him in a way that makes heat pool in inconvenient places. "I adore you. I am weak for you. When I first saw you I wanted you, and then when I got to know you that want became so intense I could not sleep for it. If anything, anyone came between us or Maker forbid tried to take you from me, I would tear a thousand holes in the Veil before letting it happen."
Fenris leans up to brush his nose against his, then puts his lips close to his ear. "Please do not tear the Veil, Garrett," he mutters before kissing him hard. The mage groans softly into his mouth and reminds him, with a delicate brush of tongue against his lips, that there is nothing he need fear here. He is in control, even beneath him; he has the power, even if he relinquishes some of it.