In a world full of immortals and mortals, the Forest of Burzee received an abandoned infant which is found by the nymphs. And Necile who wishes, even though it is against the law, to spare the child and raise it as her own. Ak, the Master Woodsman reluctantly allows Necile to take in the baby and name him Claus.
As he grows older Claus befriends the creatures of the forest and Ak shows him the children of the world who he has sympathy for. When Claus reaches adulthood, he leaves the Forest of Burzee and travels to the country called the Laughing Valley where he builds his own home abd receives a cat called Blinkie where he makes a wooden version of and gives it to a boy lost in a snow storm. The Ryls give him paint that they use to colour flowers so Claus can paint his toys. He later makes a variety of wooden animals who he decides to give to the children who are either rich or poor including Bessie Blithesome and Mayrie.
An evil army called the Awgwas realize the toys are making the children less naughty so they attempt to stop that by kidnapping Claus and dumping him in the jungle, trap him in a blocked cave and steal the toys from the children forcing Claus to seek shelter.
After violating Ak's warning to leave Claus alone, the Awgwas declare war on the immortals. In order for Claus to still make the children gifts, the immortals have no choice but to engage the Awgwas in battle. In the battle against the Awgwas and their allies the Asiatic Dragons, the Black Demons of Patalonia, the Giants of Tartary, and the Goozle-Goblins. The fiery breaths on the Asiatic Dragons were turned on them by the wands of the Fairies causing them to shrivel up and die. Some Giants of Tartary were stabbed in the flesh by the Knooks' spears. The Goozle-Goblins were stabbed in the heart by the Ryls' sticks. The King Awgwa was sliced in half by Ak while the Wood Nymphs turned his subjects into clods of dirt. While it was never mentioned what happened to the Black Demons during the battle, Ak observed the remaining Giants of Tartary retreating back to Tartary.
Soon, two reindeer called Flossie and Glossie who assist Claus to deliver the toys to the children of the world. They also help Claus to figure out how to get into the houses by going down the chimney. Later more reindeer, named Racer, Pacer, Reckless, Speckless, Fearless, Peerless, Ready, Steady and Who, come to assist Claus. The people of the world also make it easier for Claus to deliver presents by hanging the first stockings on the mantle pieces above the fire and start putting up Pine Trees as the first Christmas Trees.
Years pass and Claus grows old and comes to the end of his life so when Ak holds a meeting to decide if they should make Claus immortal they all vote in favour of it. The Immortals come to Claus's house just in time to stop the Angel of Death from taking him away then place the Mantle of Immortality on Claus.
Centuries pass and Claus faces difficulties in delivering presents to the children of the world including the people replacing fireplaces with stoves or houses without chimneys. The Nymphs and Fairies therefore travel with Claus to go through the walls so he can still deliver the gifts. The Centuries pass and the number of children increase which doesn't bother Claus as he claims "The more the merrier!" and continues his career for generations to come.

Question: Why do the immortals engage in battle with the Awgwas?
Answer: They engage in the battle so that Claus can continue to make toys for the children.
Alternative answer: They didn't listen to the warning to leave Claus alone.