Synopsis from Wikipedia

Versions of the story often begin with the creation of the world and a compacted pre-history of Tibet. This is followed by a brief traditional account of how Tibet was converted from barbarity to Buddhism under the three great Dharma Rajas (Tibetan: chos rgyal) of the Tibetan Imperial Period (7th-9th centuries AD), in particular by the great magician and founder of Tibetan religion, Padmasambhava (Tibetan: padma ‘byung gnas), who subdued Tibet’s violent native spirits and bound them by oath. It is then explained how later on the world in general and Tibet in particular, fell into a state of anarchy, since the many negative spirits and demons of Tibet had not been fully conquered. As a result the world came under the dominion of hordes of flesh-eating and human-eating demons and goblins, headed by malignant and greedy kings of many kingdoms.

In order to remedy this situation, various gods-on-high, including Brahma (Tibetan: tshangs pa dkar po) and Indra (Tibetan: brgya byin) in concert with celestial Buddhist figures such as Padmasambhava, and both cosmic and abstract tantric deities such as Amitabha (Tibetan: ‘od dpag med) and Samantabhadra (Tibetan: kun tu bzang po), as well as the spirits below the earth or nagas (tib: klu), decide that a divine hero must be sent from the heavens to the land of men to conquer these evil sovereigns. It is decided that the youngest son of Tshangs pa or brgya byin (the Gesar texts tend to conflate Brahma and Indra), should be sent. He is known by various names in various versions, sometimes thos pa dga’, sometimes bu tog dkar po, but perhaps the most universally used is don grub. This god-child is not very keen on his mission, and tries to evade it, but eventually agrees.

He is then born, with various celestial companions, and after singing to his mother from the womb, asking the way out, as the son of ‘Gog bza, who is sometimes depicted as a beautiful naga princess captured from a neighbouring tribe, but in other versions, is an old woman, and of Seng blon, who one of the respected elders of the Kingdom of Ling, which in most Tibetan versions is located in eastern Tibet (Tibetan: mdo khams), and often located specifically between the ‘Bri (Yangtze) and rDza (Yalong) rivers, which is where the historical kingdom of Lingtsang (Tibetan: gling tshang) existed until the 20th century.

The hero has an older half-brother called rGya tsha, who is a brave warrior and important figure in the epic. He is sometimes said to have been the grandson of the emperor (Tibetan: mi chen, literally: “big man”) of China, and is killed in the battle with the great enemy of Ling, Hor (often identified by Tibetans with Mongolia). This struggle between Ling and Hor is the central and most important part of the epic.

The young hero has two uncles. One is the wise and very aged elder of Ling, known as the “old hawk”, sPyi dPon rong tsha. He supports the child as he has received divine prophecies indicating his importance. The other uncle is Khro thung, a cowardly and greedy rascal, who sees the child as a threat and tries to do him ill. Khro thung is normally a comic character in the epic, but his role as the provocateur of many incidents is absolutely central.

The hero as a child grows precociously and vanquishes various diverse foes that present themselves. His behaviour is wild and fearsome, and soon he and his mother are banished from Ling. They go to the deserted lands of the land of rMa (the upper Yellow River) where they live a feral life, and the child is clothed in animal skins and wears a hat with antelope horns.

When the child is twelve a horse race is held to determine who will become the King of Ling and who will marry the beautiful daughter, ‘Brug mo, of a neighbouring chieftain. The hero-child, who in many versions is known as Joru during these early years, returns to Ling, wins the race, marries ‘Brug mo, and ascends the golden throne. He thenceforth assumes the title “Gesar”.

Once he is king, his first major campaign is against the man-eating demon of the north, Klu bTsan. While he is on this campaign, his wife is kidnapped by Gur dKar (literally: “white tent”), the King of Hor. When Gesar returns from a long absence to find this out, he uses his magic to enter the king of Hor’s palace, kills him and retrieves his wife.

These two episodes – (the demon of the north, and the war with Hor) constitute the first two of four great campaigns against “the four enemies of the four directions”. The next two are King Sa dam of ‘Jang (sometimes located in Yunnan), and king Shing khri of Mon (sometimes located in the southern Himalayan region)

After this he goes on to defeat the “18 great forts”, which are listed differently according to different versions and different bards, but nearly always include, sTag gZig (Tajik), Kha che (Muslim) adversaries. Many (in fact an open-ended number) of other “forts” (Tibetan: rdzong) are defeated besides, sometimes listed as forty.

When Gesar reaches his eighties, he briefly descends to Hell as a last episode before he leaves the land of men and ascends once more to his celestial paradise.