Dagor Ostlos
It all started when Elros shoved a handful of snow down the back of Elrond's neck, inside his cloak and tunic.
Elrond shrieked, and tackled his brother into the mounded-up snow at the side of the street. Gil-galad stood aside, mouth twitching into a grin, while Huor, his wolfhound, barked at them. It was nice to see Elrond acting his actual age for once, instead of being more serious than half the loremasters.
Elros broke free of his twin and leapt up. He only got a few steps before he tripped over the helpfully outstretched foot of Elrond's guard. This was followed by Elros' guard throwing a snowball at his opposite number. The man ducked…
And Gil-galad got a faceful of snow.
"I didn't mean to hit you, Your," – it is rather hard to speak with a mouthful of snow, as the man discovered when snowballs from Elrond and Gil-galad's guards hit him, followed by Huor tackling him into the snowbank.
"Too late," said Gil-galad cheerfully. He hurled his own snowball at Elros.
"Much too late," agreed Elros, hurling snowballs at both the elven king and his brother. One missed, and hit a woman standing by a stall that sold roast chestnuts.
A minute or so later and Gil-galad found himself ducking down behind the snowbank beside Elros, Elrond, a couple of guards, and an over-excited hound, taking refuge from a hail of snowballs from across the street, where a group of edain merchants had their snowy lair.
But they were far from beaten. "Look at the snow on that overhanging pine. Let's all aim for it at once," said Gil-galad. "One, two, three", and a hail of snowballs hit the tree, causing a cascade of snow to land directly on the merchants. There was wailing and gnashing of teeth as the merchants dug themselves out of the resulting pile.
Unfortunately, the snow also landed on some Laegrim. And so the battle of the snowballs spread. Gil-galad soon lost track of how far, being rather busy being chased through the trees by some of Oropher's warriors.
Meanwhile, over the other side of the encampment, Celebrimbor's first realization that something was off came when he heard the yelling. Leaving the plans for the new forge on the table, he left his tent, grabbing his sword from habit as he did so.
He opened the flap, and received a snowball to the chest from Tori the dwarf. Celebrimbor gawked at him. "Tis a fine snow battle my lord, come join us!" said Tori. Celebrimbor shook his head, but tucked his sword back in the tent before joining Tori in building a snow fort to keep the bakers at bay. The famed Khuzdul battlecry of "Khazad, Khazad ai menu!" rang out, along with less well-known cries best translated as "Have a snowball! Have two, they're free!"
And still the battle spread. Half a mile away, Eonwe and Arafinwe turned at the sound of screams from the encampment of the people of Middle-earth. They both paled, and Eonwe abruptly vanished, reappearing in the elves section as near to their High King as he could manage.
Eonwe had thought to protect himself with a shield of force, which was immediately tested by an enormous wolfhound. The dog bounced off, yelping and moving to stand a few feet away from the shield. Behind him, several elves and the peredhel twins skidded to a stop, including the High King, his face flushed, eyes bright, clothing soaked, and hair a tangled mess.
"What in the name of Eru is going on here?" demanded Eonwe.
"It's a game, Lord Eonwe," explained Gil-galad. "It's called a snowball fight. We pelt each other with snow, and yell a lot. Don't they do this in Valinor?" His grin widened. "You should try it, it's fun." He turned his head. "Huor, down. Lord Eonwe's a friend."
"Thank you for the offer, but I think I'll pass," said Eonwe, returning to Arafinwe's side.
"What is it?" asked Arafinwe.
"A snowball fight, apparently," said Eonwe. "They're all running around like maniacs, and pelting each other with snow. Your great-grandson seems to be enjoying himself."
"Well, at least he is acting his age for once. They grow up far too fast in Endore."
The Dagor Ostlos didn't make it into Eonwe's official report to Manwe, but Olorin told his friends about it later, having thoroughly enjoyed the whole affair, especially the part where Cirdan tripped over a rope and fell in the sea, pulling Olorin in after him.
A/N:
Dagor = battle
Ost = fortress
Los = snow
Unfortunately, I couldn't find a word for snowball.