I have officially climbed onboard this ship and this is my effort toward sailing it. I do not own OUAT, otherwise Captain Swan would be canon by now.
Starts from 2x09 and diverges from there.
"The compass, get it!" Snow ordered, already loading another arrow into her bow. Emma nodded, tightening her grip around the sword she'd acquired, and dashed around the edge of the portal, ducking the fireball Cora carelessly lobbed at her head. She raised her sword and swung it at Hook, who caught it with his own. She swung again and when he blocked the blow, Emma reared back and kicked him in the chest.
The pirate staggered backward, but when she slashed at him overhand, he did a fancy twirling thing and her sword went flying into the sand. Emma lunged at him and he used her own momentum against her to slam her to the ground.
Hook planted his sword in the ground and grabbed at her ankle as she attempted to crawl toward the dropped weapon. She scrabbled, then rolled, once, twice and suddenly the ground was disappearing from under her.
She felt Hook brace against her weight, but his boots slipped in sand slick from the portal's spray and they tumbled together into the portal. The whirl of magic, thicker than water, caught them up and they were swept in one wide circle before greedy tendrils grabbed at her and snatched her down.
Emma's world went black, and she didn't even have time to cry out.
Cora turned at the scream, choked off halfway-through, that issued from the portal, and Mulan took the opening and stabbed her ruthlessly. The witch went down with the blade where her heart should be, pinned to the ground by the sword.
She snarled and raised a hand that refused to glow. "What?" she managed out.
"The sword blocks your magic," Mulan told her. The warrior reached down and ripped off the small leather satchel hanging from Cora's hip, cradling it as though it was the most precious thing she had ever come across.
"Aurora needs her heart," Snow said. The queen had yet to turn away from the swirling portal, even as Cora struggled fruitlessly behind them and cursed their families for generations, from their ancestors to their descendants a hundred years from now.
Mulan stretched out a hand, hesitating a beat before letting it rest on the queen's shoulder. "Emma is as strong a warrior as any I have fought beside," she told Snow, "if there is anyone who can survive whatever the portal has done to them, it is your daughter."
The other woman nodded and turned to her. "Go, give Aurora her heart."
Mulan nodded and hurried off and Snow turned to the fallen queen. "Where is she?" she snarled.
Cora managed a laugh despite the fact she was fighting the metal through her chest. "I have no idea," she confided, "but it isn't your precious Storybrooke."
Snow leaned on the sword vindictively and stalked away to stare down at the portal, finding the compass and turning it over and over in her hands. Behind her, Cora tried her best to persuade the queen, but Snow simply ignored her, drowning in the detached feeling that she had only felt once before, when she walked into the nursery and found Charming bleeding out on the floor.
After what felt like ages, Mulan and Aurora reappeared through the bushes, the latter with her cloak wrapped tightly around herself as though she was cold. The warrior crouched next to Cora and examined the blade through her chest while Aurora joined her at the portal's edge.
"I'd like to come to Storybrooke with you," Aurora ventured after a long moment.
Snow shot her a startled glance. "What about Phillip?" The girl their world had named Sleeping Beauty had been determined there was a way to bring her prince back and she was going to find it.
The brunette tugged her cloak tighter about herself and cast a nervous glance at Cora, who was having rocks piled on top of her by Mulan. "I learned more than Cora wanted me to when she had my heart," she confided, "there is no way to retrieve a soul consumed by a wraith, any more than there is a way to lie in the presence of a gryphon."
Snow pulled the other woman close, offering what comfort she could. Aurora buried her head in Snow's shoulder and they stayed that way until Mulan ran up to them, sword back in its sheath at her hip and Cora fighting to get out from under the rocks. "Let's go," the warrior said.
Wordlessly, Snow extended the hand with the compass. Aurora laid a hand on it and Mulan wrapped an arm around the princess's shoulders before grasping onto the gleaming metal. All together, they leapt into the portal.
They fell for what might have been seconds and might have been hours, dragged along by the compass. All around them was darkness, the light from the Enchanted Forest fading rapidly until a spark of light shot up in front of them. As quickly as the darkness had descended, it was gone, and the portal spat them out over the edge of the wishing well.
"Grandma!" Henry's hug nearly took her off her feet just as Snow was getting them under her. She clutched him tight, trying to postpone the inevitable moment when he discovered Emma was gone and glanced around. Regina was doubled over, leaning against a tree as though that was the only thing keeping her upright, and Rumplestiltskin was slinking away as sneakliy could. Snow made a mental note to ask Henry what the Dark One had done later.
"Henry?" Aurora's voice served as a distraction, and her grandson was all too happy to hug Aurora too.
"Snow!" Red's greeting was nearly as enthusiastic as Henry's, though she noticed her old friend was limping just slightly as the wolf-girl embraced her.
"Where's Charming?" she asked frantically.
"Gold's shop," Red replied. When Snow hesitated, her friend gave her a small shove. "Go, I'll deal with your visitors."
She needed no more encouragement. The town passed in a blur and the dwarves made way for her. For just an instant lingering over him she hesitated, the memory of the fire-room sweeping her up, then she fought it back, set a hand on either side of his face and swooped down to kiss her love.
Magic, dizzying and heady, filled her from head to toe, making her feel lighter than air and brighter than the sun. It was a glorious feeling, made better only when she pulled back and Charming opened his eyes.
"You found me," he said, repeating her words to him from that glass coffin.
Snow couldn't stop the laugh that bubbled up, running her thumb over the scar on his chin. "Did you doubt I would?" she teased, echoing his line.
"No," he answered, and sat up to kiss her properly. This, being in his arms at last, both of them alive and whole and finally together, was better than any curse-breaking magic could possibly be.
"Though the room of fire gave me pause," he finished when they broke for air.
Snow laughed again and cuddled close, noting in a corner of her vision that Henry had entered the room, the dwarves pressing aside to make room for the last member of their family. He climbed straight up next to them; Snow slipped sideways to sit on the bed rather than in her husband's lap, freeing one of Charming's arms to wrap around his grandson.
"My mom didn't make it, did she?" he asked in a wavering voice.
Snow felt suddenly horrible. She should have told Henry the whole story before going to wake her prince, but she had been desperate to see him, save him from that horrible burning room, assure herself he was still alive and whole.
"Oh, Henry," she reached across to take one of the boy's hands, "she's not dead. Emma fell into the portal."
He looked up at her, warm brown eyes swimming with unshed tears. "She's gone?"
"Hey," Charming shook his grandson lightly, "we're family. We'll find her, don't worry."
Emma opened her eyes to blackness more complete than anything she had ever seen.
"Oh good, I was beginning to fear you'd never wake lass."