Morningstar
He had said it once, to Voldemort, and had never been allowed to forget it. I regret, my lord, that I have only one son to give for my country. He had not meant it then, and he did not mean it now; if anything the opposite was true. He would have given any number of countries to keep Draco safe. He sat at the head of the table, at Voldemort's council of war, and the white smooth parchment under his hands was no whiter and no smoother than his son's skin. He received the tribute from wizarding colonies across the sea and the silver was no brighter, no finer, than the silver of Draco's eyes. He led a raid on Hogwarts at moonrise, and the triumph of victory was nothing to the triumph of fatherhood.
He had said it once, quick careless flattery, words meant only to amuse. They followed him everywhere; they might have been branded on his arms, twined around the Dark Mark. I regret, my lord, that I have only one son to give for my country. His wife taxed him with it; his leader mocked him for it. It was as if the words ran at his heels with his hellhounds. He heard them even in his sleep.
Voldemort was lost, and with him the war. Lucius spent three months in Azkaban and was set free to watch his son grow up. He felt like Abraham, reprieved at the altar with the knife in his hand. Draco was quick and clever, generous and ruthless in turns, the kind of son any man would be proud to have. Lucius loved him the way he had never loved anyone or anything, more than he had ever dreamed he could love anyone. Draco made him capable of love, capable of kindness. And still the words haunted him, only one son for his country, echoing like the scream of an animal sacrificed in the dark. His own words, his pride and his foolishness.
If his words cost him his son, it will kill him. He can imagine how it will be: Voldemort in his great throne-like chair, and Lucius himself at his lord's right hand. McNair and Rosier will drag Draco in and throw him at Voldemort's feet, and Draco will not even struggle because he trusts his father to save him. Lucius has always saved him. Lucius will try to stand, only to find he is Petrified, his arms sealed to the arms of the chair. Voldemort will make him watch as they cut out Draco's heart and wait for him to die, all for a fool's promise made long ago.
One son, one country, one sacrifice, one careless, solemn vow. The best Lucius can hope for is to die before the war begins. One way or another Voldemort will take Draco from him. And Lucius will have no- one to blame for it but himself.