At first, Twilight mistook the low rumble for thunder.
A glance to Rainbow challenged that theory. The weathermare’s eyes had narrowed and wings flared. Half-risen from the train seat, she bore no sign of the ready confidence with which she would face a storm, instead tensed against some unknown threat.
In the next moment Twilight noted Pinkie’s pupils had shrunk and her body was trembling, held more rigidly still than she had ever seen.
It was all the warning she had before with a sharp crack the world lurched under her, the car of the train tilting inexorably onto its side. It felt slow - mockingly slow - and yet she barely had time to meet her friends’ eyes before it fell. Fell and did not stop - everything began to spin increasingly quickly as she was thrown unceremoniously against their luggage, bruised and battered, train car gaining momentum as it rolled down a steep slope -
Her horn lit in panic, magic enveloping her friends to drag them from this metal deathtrap and onto solid ground. The energy of arresting their momentum in the teleport dug a trench into the hard-packed snow, enough to secure footing, as the train car crumpled on the rocks below them.
The relief that washed over her to not be on it proved short-lived. Twilight’s ears flattened back against her head as she looked up - and wished they’d never left.
Icy chunks rolling towards the group from above, somewhat obscured by a billowing white cloud of snow, attested Twilight had teleported the group straight into the path of an avalanche.
“Gah! Somepony, give me a boost!” Spike and Rainbow wasted the least time in responding, dragon leaping onto the quick pegasus and both charging to breathe dragonfire over the cold threat. Green fire lapped impossibly broad at the avalanche - and steam hissed as the ice evaporated from still-tumbling rock. Rainbow dodged several forerunners in order to herd the constructed cloud at breakneck speeds outrunning the avalanche, handing the rapidly cooling water cloud off to Rarity and Fluttershy in her passing.
“What are we supposed to do with this, darling?” Rarity’s voice was a thin veneer of calm over building panic, but she kept her poise. Immediate mortal peril was not truthfully her preferred time for theatrics, appropriate as they would be. The raw fear in Rainbow’s response, though, belied her quick response.
“I don’t know! Make something!” Running out of the cushion of warm air provided by Spike’s flames, Rainbow slowed and turned to aid Fluttershy in pushing the cloud to the ground. A strange sense of deja vu came over Rarity as she called on talents she did not remember using to wrap her magic around the clouds and began to sculpt; despite the unfamiliarity there was something approaching practiced ease to it. Soon the ground was slippery with ice where the cloud condensed and melted the snow, shaped in an abstractly floral design to channel the rocks away from them. Spike jumped down beside Rarity to give aid with precision firebreath in resculpting the channels, maintaining the icy perimeter.
Applejack’s lasso snaked out from a ledge the earth pony had claimed when the first large rock proved too hefty to be swayed by the defense of ice, yanking it to the side to tumble away harmlessly. Planted firmly on the ground, staring a challenge at the earth itself as it sought to crush them. Pinkie on the other hoof popped up beside or on top of the pieces, displaying some of the talent of her rock-farming heritage as she tap-danced a boulder into an explosion of harmless confetti. Despite their strength and agility, there were still too many for them to fend off, and Twilight’s horn sparked again - calling on a more directly defensive magic, this time, enough for a shield as she braced for impact.
Red shield springing up around her and her friends, the impact of rocks on her magic caused her to wince, but she held firm, though her voice cracked with her next instruction. “Shelter! Get shelter. I won’t be able to hold this long once there’s a mountain on it.”
“On it, sugarcube. Spike!” Applejack called the dragon to her as she set her hooves to further digging shelter from the hollow they’d wound up in. Spike rushed to her side, aiding her in melting deeper into the ice and forming something of a cove. At Twilight’s urging everyone but her huddled into the makeshift cave - barely making it before the overwhelming weight of the avalanche finally overwhelmed her shield.
She found comfort knowing that she’d kept her friends safe as she could have, before the mountain crushed her.