This was the reward which the gods gave to courage. When a hero had
gloriously lost his life, the Valkyries, the nine warrior daughters of
Odin, brought his body up to Valhalla on their white horses that gallop
the clouds. There they lived forever after in happiness, enjoying the
things that they had most loved upon earth. Every morning they armed
themselves and went out to fight with one another in the great
courtyard. It was a wondrous game, wondrously played. No matter how
often a hero was killed, he became alive again in time to return
perfectly well to Valhalla, where he ate a delicious breakfast with the
Jisir; while the beautiful Valkyries who had first brought him thither
waited at table and poured the blessed mead, which only the immortal
taste. A happy life it was for the heroes, and a happy life for all who
dwelt in Asgard; for this was before trouble had come among the gods,
following the mischief of Loki.

This is how the trouble began. From the beginning of time, the giants
had been unfriendly to the Æsir, because the giants were older and huger
and more wicked; besides, they were jealous because the good Æsir were
fast gaining more wisdom and power than the giants had ever known. It
was the Æsir who set the fair brother and sister, Sun and Moon, in the
sky to give light to men; and it was they also who made the jewelled
stars out of sparks from the place of fire. The giants hated the Æsir,
and tried all in their power to injure them and the men of the earth
below, whom the Æsir loved and cared for. The gods had already built a
wall around Midgard, the world of men, to keep the giants out; built it
of the bushy eyebrows of Ymir, the oldest and hugest of giants. Between
Asgard and the giants flowed Ifing, the great river on which ice never
formed, and which the gods crossed on the rainbow bridge. But this was
not protection enough. Their beautiful new city needed a fortress.