Battle of Wailing Fen

Through confluence of wind and ill fate, the enchanted mists about the Shrouded Shore billowed and thickened. As they grew ever more dense, their accumulated magics shone like a beacon within the Realm of Chaos. Thus did Daemons find purchase upon the lands of Yvresse.

The Elves met the daemonic host on the outward edge of Wailing Fen. Moranion of Athel Tamarha rode at their head. He was owed many favours by princes of other lands, and so the tall spearmen of his holdings were joined by warriors of Chrace, Eataine, and even further afield. Moranion would need all their skill and valour in the hours to come.

At the battle's height, a Bloodthirster descended from the skies, roaring and bellowing as it carved bloody ruin through a regiment of White Lions. The woodsmen of Chrace fought on, even though they knew that they were overmatched. Their fortitude was soon repaid with salvation: a Flamespyre Phoenix, fire streaming behind, dove out of the darkness to rake the Bloodthirster with its mighty talons. With a thunderous crack, the Daemon's whip lashed out, coiling around the firebird's neck. The Phoenix shrieked in fury as its mighty wings strove in vain to bear it aloft once more, but the Bloodthirster was too strong. Oblivious to the White Lions' axe-blows, the Daemon hauled the beast close and tore out its throat with savage fangs. Casting the Phoenix's corpse to the ground, the Bloodthirster roared in triumph.

Yet the fires of the fallen Phoenix did not extinguish with its death. They continued to blaze, growing ever hotter and more furious with each passing moment. The White Lions fell back as their cloaks caught alight, but the Bloodthirster, maddened with gore-lust, came on through the flames. Three steps had the Daemon taken when there was a thunderous boom; the Phoenix's body exploded in a shower of smouldering plumage, and a column of fire spiralled into the sky. Caught at the conflagration's heart, the Bloodthirster's flesh blackened and cracked but, insensate to pain, it came on, hungry for blood. Indeed, so intent was it on claiming the skulls of the remaining White Lions, that it did not notice the flames draw together and coalesce into a new form - the Phoenix reborn.

It took but a moment for the Flamespyre Phoenix to sight its erstwhile slayer and, giving out a great shriek, it dove to the attack. On hearing the cry the Bloodthirster turned but, before the Daemon could bring its weapons to bear, the Phoenix was upon it once more. Talons sank deep into the Bloodthirster's shoulders and an iron-hard beak punched through the Daemon's armour to pierce the black heart within its chest. With one last bellow, the Daemon's mortal form perished, and its spirit was cast back into the Realm of Chaos. With this final blow, the battle was won. As the Bloodthirster fell, the magic sustaining his army began to unravel. The Daemon army faded back into the mists, and peace fell upon Yvresse for a time.

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