A/N: Apologies in advance. This idea occurred to me a few days ago and I had to write it down. I believe this will be the first (and for a while, possibly the only) Frozen/Avengers crossover.

Spoilers: For both universes, obviously.

Prologue

Standing atop the icy fjord, the winds die completely. Every snowflake hangs in the air in a beautiful mockery of her sorrow. Her legs fail her; she collapses to her knees in her grief. Anna is dead.

Hans is speaking, condemning her to death, but she pays him no attention. She knows that she is going to die - she welcomes it, that she might see her sister again. Anna is dead.

Hans has stopped speaking. An icy tear slides down her cheek. Her greatest fear has come true; she is responsible for the death of the only person who matters to her in the world, Anna. A metallic screech, a sword being freed from its sheath, pierces the brief silence, and she knows her time has come. A thousand thoughts bubble to the surface as regrets and sorrows flood her mind. Anna... Anna is dead.

Without warning she hears a cry that can only be her sister. Time seems to stop but she cannot react - her sister is moving to shield her from the falling blade. Her sister now stands before her, between her and her executioner, rapidly solidifying into ice. Anna is alive?!

A sharp clang of metal is heard as the blade meets ice. Brittle, fragile ice snaps, cracks, shatters; pieces of what were her sister fall all around her. She feels a single shard of ice - Anna - fall into her left hand. Anna - sweet, innocent Anna. Anna is dead.

Anna is DEAD.

Gripping the shard of ice, once her sister, in her hand she stands as the wind picks up. Icy sheets rise and fall with her breathing. Flurries of snow give way to a blizzard - she feels her hair whipping at her face as she stands, her eyes boring down on the man whose blade shattered her sister. A cold rage grips her as the swirling storm continues to build. A single refrain repeats in her mind. Anna is dead.

Arendelle was lost that day, buried in the Summer Snowstorm. Legends would tell that it was the young Queen herself who cursed the kingdom to an icy grave. The Glacier of Arendelle, the land where Arendelle once sat, was blanketed with permanent winter.

A kingdom engulfed in the fury of the Snow Queen.