One word described that moment: safe. The twins lay cuddled with one another as usual, their mother lingering above them tenderly.

"Good night, my little sandpipers," cooed Elwing. She pressed a kiss to the crown of each head. The rhythm of the snoring waves matched her warm, soothing breath.

"Love you, Nana," Elrond and Elros replied in dreamy unison.

"I love you t—"

The scream of a bronze trumpet rent the purple comforter of night.

In a daze, the twins bolted upright. "What's that noise?!?" they wailed.

Elwing clenched her teeth. She'd feared this moment.

"MY LADY!!" Cirdain thundered up the steps to Elros and Elrond's nursery. "FLY! FLY!"

"What's going on!?" Elwing shrieked, though she knew full well.

The door burst open. Cirdain, his armor barely fastened on, dashed in. "The Kinslayers," he panted. "The boys—get the boys out of here!" he grabbed Elwing's arm and urgently hissed in her face.

She nodded tersely, yanked the weary, confused twins out of their warm bed, and ran.

Already, bells boomed, horns blared, and fire raged across the once peaceful port. People screamed. Bewildered guards dropped dead before they could scramble to arms.

Four powerful voices boomed above the city's din as one: "FOR THE OATH! FOR THE SILMARIL!"

Elwing knew she had very little time. The reserve of soldiers in the palace were already arming. Cirdain had told her to run, and she did.
She ran past panicked servants, under frantic guards, through countless halls, and into a small, dark room.

Elwing shoved her sons into a corner. "Do. Not. Move."
Her bewildered twins shuddered in a corner as she desperately lit one of the unused torches on the wall. The fire cast a kaleidoscope of light as the flames refracted off the many faces of every jewel in that room. None were what she looked for. Flames swooshed as Elwing moved the lit torch this way and that. Finally the dim light revealed her prize: a small wooden box with none of the usual elvish filigree. Elwing yanked out a little key from her pocket. Her anxiety made the seconds drag, until the key finally made a melodious little click!  When she cracked the lid open, Elwing found the source of literally millennia's worth of carnage: a Silmaril, one of three created by Fëanor, disgraced King of the Noldor. Hastily fastening the necklace that housed the jewel onto her neck, Elwing grabbed her son's hands again and ran.

As she desperately tried to take her sons somewhere safe, she heard the cries of war bellowing below, as the Fëanorian forces tore down the palace gates.

"FOR THE OATH! FOR THE SILMARIL!"

The creative juices are flowing now! Due to the nature of the source material, expect a little description for, shall we say, the fortunes of war? I will try to keep the chaos relatively general, though.