Battle of Finuval Plain

In the year 139, of the 11th Phoenix King, the fate of Ulthuan hung in the balance once more. The Dark Elf army was large beyond counting, bolstered both by fell allies from the Old World, and by the Witch King's terrible sorceries. Yet the High Elves possessed the courage of desperation -- they knew that defeat here would doom not only their fair land, but also the entire world.

Wrathful at the failure of his Assassins to slay the Everqueen, the Witch King loosed the Daemon N'kari to hunt her down. Tyrion held the Keeper of Secrets at bay, but the prince was overmatched and saved only when Teclis arrived and banished the Daemon to the Realm of Chaos. Cloaked by Teclis' magic the trio reached the shores of the Inner Sea. There, a white ship crewed by the remaining Handmaidens of the Everqueen carried them to Finuval Plain, where the shattered remnants of the Elf armies were assembled to make a final desperate stand.

As the battle raged, monstrous Cold Ones were hamstrung by nimble Shadow Warriors, and poisoned bolts ricochetted from the armour of Caledorian Dragon Princes. Khainite Assassins plied their bloody trade, striking down princes and mages wherever the High Elves gained advantage. Phoenixes swooped through rank of Witch Elves, the roiling air of their wake setting hair and flesh ablaze. On the right flank, plate-clad Chaos Warriors exchanged blows with Swordmasters of Hoeth, and White Lions hacked at Slaughterbrutes and winged Chimerae. All about, spells crackled back and forth through the air, and blood mingled with the dust thrown up by battle. Thousands died, but neither side gave any ground. So great was the carnage that warriors fought over the bodies of the dead, and raves feasted upon the wounded trapped within the mounds of corpses.

Tyrion fought in the very center of the battle, striving with the fury of an enraged beast. His great burning blade cut down foes with every stroke, and where he rode, the High Elves took heart. Meanwhile, Teclis wrestled with the Witch King's dark sorcery, and for the first time, encountered a foe that was his match. Lightning streaked across the darkening sky. Terrible clouds of black sorcery, capable of stripping warriors to the bone, were turned aside by magical winds. Daemons tore their way through to the mortal world and brought fresh carnage to a battlefield already heavy with slaughter. This alone might have spelled doom for the Elves, had it not been for the actions of the Everqueen, who sent sent a wave of blazing light through the daemonic ranks, casting many thousands of them from the mortal world. Alas, this deed saw her already waning powers completely spent; moments after, her unconscious body was borne from the battlefield by her surviving Handmaidens.

It soon became clear that even the deeds of heroes could not overcome that dark host. Tyrion could not be everywhere at once, and Teclis could not halt every spell. Slowly, the weight of numbers turned against the High Elves. Teclis saw that the battle had turned, that the High Elves would be massacred if something desperate was not attempted. Gathering his strength, Teclis invoked the power of Lileath, his staff glowing with brilliant light as the goddess fed him energy. With one final effort, Teclis sculpted the power into one titanic burst, and unleashed it upon the Witch King. Frantically, the evil one tried to turn Teclis' assault aside, but he could not. The blast descended upon him, burning into Malekith's twisted soul. At the final moment, he was forced to hurl himself into the Realm of Chaos to avoid utter and final destruction.

Freed now from the burden of dealing with the Witch King, Teclis turned his sorceries upon the evil horde. Magical flame sprung up amongst the Dark Elf ranks and bolts of pure magic thundered from the heavens. Through the maelstrom of sorcery rode Tyrion, his sword-arm weary, but his wrath unabated. With a single mighty blow, the Elf prince cut down the Witch King's standard bearer, and his steed trampled the fallen banner into the mud. Seeing their dread lord defeated, the Dark Elves fell into despair and withdrew from the field.

In the wake of the battle, Tyrion led the army south. The vengeful High Elves fell upon the besiegers of Lothern, putting them to the sword even as Phoenix King led a sally from within the walls. Caught between hammer and anvil, the invaders were utterly crushed. Two days later, the High Elves went on the offensive. Tyrion led an army to relieve the Tower of Hoeth, whilst the Phoenix King took another northward, to directly confront the main Dark Elf host. For his part, Teclis took ship overseas, bringing aid to the embattled Old World, for the Elves knew well that if the kingdoms of Men fell, then the hordes of Chaos would soon turn their attention again to Ulthuan's shores. Though the war was far from over, the tide had turned.

Source

 * Warhammer Armies: High Elves (8th Edition) -- pg. 28-29