This scene takes place during Joceyln and Luke's wedding in City of Heavenly Fire
Jocelyn looked so happy on the dance floor as Luke twirled her around to the rhythm of the music. Her white wedding dress (she chose white for mundane customs) flowed across the floor like a white wave, and she reminded Alec of a graceful swan on the lake.
"Luke must be the happiest man alive," Magnus approached him, a glass in either hand. "You can see it in his eyes. Champagne?"
Alec took a glass, watching as Magnus snapped his fingers over the drink and it began to fizzle with blue sparks. "I don't blame him. Jocelyn is an amazing woman. She'll make him happy."
The music changed to another slow song, and this time it was for everyone to dance to. Luke placed a hand on Jocelyn's waist and held her hand with the other, while Jocelyn rest her head on his chest. Even Jace and Clary were on the dance floor, smiling at each other and whispering quietly.
"Well, would you look at that. Your sister is dancing with the vampire Salmon," Magnus chuckled and took a sip of his drink.
Alec scowled. "Good for her. She can dance all she pleases. Izzy loves the spotlight anyway."
Magnus frowned at the look on Alec's face. The boy looked so sad and lost that it nearly broke his heart. Setting his glass down on the table next to them, he grabbed Alec's hand. "Come. Follow me, Alexander."
Alec tried to wiggle out of Magnus' grasp. "No. What are you doing?"
"Dancing, of course. Isn't that what music is for? Especially this kind? Do Shadowhunters not dance at weddings?"
"Not really," Alec grumbled. "We more or less just have a ceremony and then move on. Mundane customs like to drag things on longer than necessary-"
"And that's why I adore mundanes. They know how to throw a party. Now shut up and dance with me."
Magnus finally managed to drag Alec out on the dance floor, despite the strange looks and disgusted glares they were receiving from the majority of the crowd. But Magnus didn't care. He was here to have a good time with Alec and nothing and nobody was going to ruin this night for him.
Alec didn't know where to put his hands. "I don't know....where do I...."
Magnus rolled his eyes. "Put your hands on my hips, Alec."
Alec's eyes widened. "You want me to put them where?"
"Oh for the love of....." Magnus grabbed Alec's hands and placed them on his hips and put his own hands on Alec's shoulders. "Here. Since I have to do everything for you. Now we dance."
The dance was a little awkward. Alec kept stumbling and tripping over their feet and spent most of the song apologizing for stepping on Magnus' toes. Magnus thought it was charming and adorable, watching his boyfriend struggle to slow dance.
"You're so cute when you stumble, Alec. It's so endearing."
"I wasn't aiming for endearing. I'm trying not to fall flat on my face in front of everyone...." Alec cleared his throat and regained his composure. "Plus people are staring. It's making me nervous."
Magnus looked around at the crowd. A few people were whispering and pointing at them. He could see why Alec didn't like it. He wasn't used to the spotlight.
"Just ignore them. Tonight is about us. We can't let a couple of Shadowhunters ruin it for us, right? Just focus on me. I'll lead."
They danced some more to the seemingly never ending slow song, only tripping once and that was only because Alec bumped into Clary. She smiled and apologized, even if it wasn't her fault. Jace just smirked at his brother and winked at Magnus.
"I think Jace just winked at me," Magnus whispered. "I'm almost tempted to leave you and run away with him instead."
Alec raised an eyebrow. "You had plans to run away with me?"
"Of course!" Magnus laughed. "If your parents didn't agree with us being together, I thought we'd elope in Vegas. Have our honeymoon in Paris. I can show you where I used to stay years ago."
Alec smiled. "That does sound nice. But I actually think my parents like you. Like us, I mean. They don't mind us being together. Especially my father. He seems very fond of you..." Alec glanced over at his father. Robert Lightwood was sitting at a table not far from them, chatting with a few werewolves. He caught Alec looking at him and gave his son a warm smile and a nod.
Magnus purred. "Yes. I'm glad your father is on board with our relationship, but it wasn't him that I was worried about. I knew Robert long before I met you-don't look at me like that. It wasn't romantic. I may or may not have babysat you once or twice when you were a toddler."
"You what?!" Alec's voice cracked.
"Shhh! It was for your own protection. Isabelle's too. I looked after you once when your parents were still hiding from Valentine. Your father asked me to watch you while they went and did whatever. I didn't ask what he was doing. All I knew was that I was getting paid. Nothing else mattered. Until now."
The song finally changed to a dance song and the crowd cheered and got up to dance. Magnus took Alec by the hand and went over to a table to sit down. Maryse eyed them as they took a seat with her, her blue eyes staring Magnus down.
"Maryse. You look absolutely stunning tonight," Magnus kissed her hand and smiled his most charming smile.
"Thank you...." Maryse blushed under the light of the chandelier. "As do you. That's quite an expensive looking suit you're wearing."
"Nothing is expensive when you're wearing it for the person you love," Magnus took Alec's hand and held it. "I've come to ask your permission to have your son's hand in marriage."
Maryse's eyes widened in shock. She looked remarkably like Alec when she did this. "I....hand in marriage?"
"Marriage?!" Alec was red in the face from blushing. "Magnus, I don't think now is the-"
"Is that a problem? I can always go over and ask Robert for permission-"
"No. It's fine. You can ask me. I just wasn't expecting it to happen so soon....when do you plan on getting married?" Maryse sat up straighter in her chair.
Magnus looked at Alec. "When would you like to get married, Alexander? It's your choice. Spring, Summer, Autumn, or Winter."
Alec ran a hand through his hair. "Uh.....I always did like the idea of an Autumn wedding."
Magnus smiled, revealing pearl white teeth. "Excellent. Just a moment, please." He went up to the stage, unplugging the DJ's stereo. The crowd groaned in protest, but Magnus ignored them as he took the mic off the stand. "Excuse me. If I could have your attention please. Thank you. I have an announcement to make. Or a proposal, really. For the past few months, I've come to know an incredible young man whose heart is made of pure gold. He cares for everyone and always puts the needs of others before his own. He's intelligent, funny even though he thinks he isn't-" The crowd chuckled at this. "And his heart in the right place. Alexander Gideon Lightwood.....would you make me the happiest man alive and be my husband?"
The crowd gasped and began to whisper as the spotlight suddenly went to Alec in the audience. He was red in the face, but a smile soon spread across his face as he nodded.
"I'd be honoured to be your husband, Magnus Bane," he said. "Very honoured."
Magnus smiled broadly as he jumped from the stage, rushed over to Alec and planted a kiss on his lips. He could hear Jace clapping and cheering, and pretty soon the entire crowd was cheering and congratulating them on their engagement.
"What about the ring? You can't get marriage runes....they'd kill you," Alec whispered once the noise died down.
"Don't worry about the ring. You said yes. That's all that matters to me right now," Magnus kissed Alec's neck. "We'll worry about that later, okay? Right now let's just enjoy the moment."
Another slow song played, and this time it was Alec who led Magnus to the dance floor. Magnus was stunned when Alec took the lead, his feet not tripping or stumbling once.
"Alexander! You didn't tell me you could dance! I'm impressed!"
"I can't, actually. I'm full of adrenaline right now. I feel like I can do anything," Alec grinned and laughed.
Magnus kissed his cheek and fixed his fiancé's hair. "You can do anything. I know you can."
Alec hugged Magnus tightly and let out a shuddering breath. "You've just made me the happiest man alive, Magnus."
Magnus closed his eyes and hugged him back. "Me too, Alec. Me too."