He looked at Draco, still crouched against the back wall, belly on the floor and arms and legs under him, scared shitless. He couldn't leave him. He made his decision. He let go and cast a Alohomora spell on Draco's cell door. He made it inside and slammed the cell door shut just as the werewolf behind the door burst into the bunker. He crashed into the bars of the cell, snarling and trying to swipe at him through the bars.
Harry sent a Bone-Crusher spell at the limb and the werewolf howled in agony. More wolves swarmed in through the opening and were smashing against the bars. Harry fired more spells, but the wolves healed and returned to clawing the bars apart. Harry was shaking from exhaustion and, as a last effort, he conjured thick stone walls, slowly covering the outside and then the inside of the bars. The wolves would need time to get through them, and also the bars in between. 
The noise was instantly gone. The wolves could barely be heard with human ears. They should be safe until sunrise. Harry backed into the back wall and slid down. He nearly sat on Draco, but the werewolf moved out of the way. Harry felt a little afraid as Draco was now looking down at him. He didn't have the strength to fight or cast another spell. He needed to save his strength to Apparate out in the morning.
Draco's head dipped, and he moved forward to lick his hand, again. Harry petted his head. "We're safe, Draco."
The werewolf whined, and his claw-like hands climbed onto his chest. The sharp claws nearly pierced through his skin.
"Ow! Watch the claws!" he grumbled, and Draco folded his fingers inward.
Harry couldn't believe that the werewolf understood him so well. Draco laid down on him, slightly more possessively than at home. Harry could feel Draco's member against his leg, but this wasn't about sex. Draco's nose found its way to Harry's neck, and his hands gently pawed at his chest as though Draco wanted to burrow into his embrace. Harry wrapped his hands around Draco, rubbing his back gently, only grazing his bitemark.
Draco whined softly and licked his neck, careful to not bite him. Harry trusted the werewolf and turned his head to open up his neck. Draco stopped whining and was wagging his butt, again. He licked more, and even lick-washed Harry's face. Again, it wasn't sexual, or Harry didn't feel it was. After Draco decided that Harry was properly claimed, he settled back into his neck. Harry just kept petting him, as the sounds from the burrowing wolves were getting louder. Draco was shaking more and more.
"I think you were right, Draco. They're never going to stop. I could have been bitten or killed. Hermione and Ron might have to come next time," he murmured. 
Draco whined softly.
"I don't want to live with the fear that our... I mean... your child will get snatched... or turned or killed. I couldn't imagine the pain of knowing what they could do to him or her. Or what they'd do to the child."
Draco patted his chest with his paw and met his eyes.
"We have to take out the pack... or... take out the leader. That new alpha even told me that they would let me take over. Plenty of the werewolf books say that the pack will follow the strongest wolf. I won't let them win. I only need to challenge the leader and win. Then I'll be in charge, and they will obey me."
Draco tilted his head, unsure.
"But... I need to be a wolf. This attack only shows how much I need to be one," Harry murmured, looking at the wall. 
He didn't want to risk waiting for another moon for them to succeed in getting Draco. He also didn't want to take the choice away from Draco, but if he waited until the next full moon, Draco could take steps to stop his plan. And Harry might need to adjust to being a werewolf.
"Draco? I'm sorry... but I'm been considering this for a while. I want to join with you... be equal to you and fight for you... for us. I make this decision... without regret. I choose you, okay?" he whispered.
Draco whimpered and bumped his hand with his nose.
Harry had no interpretation for that. He petted Draco and pulled his head up. "I want to be a werewolf. I want you to bite me, Draco."
Draco straightened up and tilted his head, considering. He lifted up and sniffed his arm. He followed it up to his chest and then neck. He licked it as though choosing his spot. The spot Draco always went to, even when he was human. Harry turned his head. It was probably a terrible place to bite, artery-wise, but he trusted Draco not to kill him. 
Draco licked him again and then opened his mouth. His teeth latched onto a small area on his neck, but he didn't bite down. He held, waiting for permission.
"Bite me, Draco," Harry said, softly.
Draco growled lightly, and then his teeth pressed hard, breaking the skin as Draco latched on for a moment and didn't let go. Harry cried out in pain, but Draco didn't dig in any further. Harry felt jolts of pain radiating outward, and his vision dimmed temporarily. Draco eventually let go and then started licking the blood away. Harry felt the change immediately as the werewolf venom spread, but he felt Draco's tongue even more. The sensation of Draco licking his bitemark was nearly overwhelming. Now, he understood why Draco enjoyed it so much. He could feel Draco's love and trust right through the bond.
Harry started shaking from the emotions he was feeling. His soul was singing from it, and Draco just kept licking. He could feel Draco's fear, too, and the pain of his memories. He could even see images of Fenrir towering over him, of the pack watching the Alpha stake his claim and even of Draco presenting himself to his cruel alpha. Harry tried to stop the flow, but wolf-Draco was intent on sharing his memories. 
More flashes of Raulf, Ryman, Scabior and the others came. Each was just as cruel as the others. Then came the familiar scene where Raulf and the other wolf were abusing him. Harry saw himself come in. He could feel the instant connection Draco had with him. Wolf-Draco recognized his power and strength... virtue. Wolf-Draco knew, in that moment, that Harry would save him.
Harry was still getting lost in Draco's emotions and memories when Draco jerked away and rolled away. He landed on his back and writhed on the floor. The moon must have set. Harry watched the hair recede into his skin, and his claws and fangs shrink. He took down a few of the wards that remained and just grabbed Draco's arm. Then he Apparated them home.