Battle of the Peak

After Gandalf and the Balrog known as Durin's Bane fell down into the chasm beneath the Bridge of Khazad-dûm, Gandalf pursued his foe through the depths under Moria and up the Endless Stair beneath Celebdil. That stair climbed up through the heart of the mountain to reach Durin's Tower at its peak, far above the clouds. Emerging from the Tower, the Balrog returned to its fiery form, and so began a climactic battle between the two Maiar.

That battle lasted for two days. Gandalf later likened it to a storm on the mountain-top, out of which rolled the sound of thunder. The battle was fought with lightning and fire and ice, until at last Gandalf was victorious. He threw the Balrog down from the peak, and where it fell, the mountain-side was ruined. Gandalf was himself utterly spent in the battle, and after the fall of the Balrog, he too collapsed into darkness and died.¹

For nineteen days Gandalf's body lay on the mountain, until his spirit was sent back to complete his mission in Middle-earth, and thus he returned to life as Gandalf the White. He was carried to Lórien by Gwaihir the Eagle, and from there he set out once again to work towards the final defeat of Sauron.