The origin of Adai’s family lineage traced back to Kadan and Hasar due to the interfamily marriages within the Borjigin clan. Mongolian sources also say Adai was a son of Örüg Temür Khan. Adai’s family was a member of eastern Mongol clans, Khorchin, originated in the region of Nen River to the east of Greater Khingan Range. Even before his proclamation as the Khagan, Adai almost succeeded in unifying western Mongol territory by defeating the Oirats. Alarmed by the possible resurgence of another Genghis Khan’s era, the Ming Dynasty provided support to the Oirats and their allies among the western Mongol clans, successfully turning the tide by first recovering and then launching counteroffensives against eastern and central Mongol clans. Arughtai Chingsang installed Adai on the throne as Khagan of the Great Yuan after discussing the matter with the family of Khasar.
Reign
During his rule, Adai was able to consolidate and expand his power, eventually unifying both the central and eastern Mongol territories in 1425. However, his conquest of western Mongol territory was checked by the Oirats and both sided continued the war for unification for decades. Riding on the success of unifying central and eastern Mongol territories, Adai proclaimed himself as Khagan with support of central and eastern Mongol clans in 1425, the same year his rival khan in the west, Oyiradai was killed. Adai and Arughtai crushed the Oirats and killed several leaders of them. After capturing the Oirat nobles, Adai, married Gulichi's wife, Öljeitü the Beauty, who had been a consort of Elbeg Khan and enslaved Bahamu's son. Although Adai Khan’s authority did not fully reach western Mongols who did not recognize him as supreme ruler, western Mongol clans did not have a khan of their own so Adai Khan remained as the sole Mongol ruler for the next eight years at least in name. Elbeg's daughter and the Oirat taishi Bahamu's widow, Samar, persuaded the Khan to release her son now named Toghan to western Mongolia. However, in 1433, Toghan raised a rebellion and western Mongols finally crowned Toghtoa Bukha with the title of Tayisung Khan as their next new khan, which resulted in half a decade of the simultaneous existence of two khans supported by opposing Mongol clans.
Decline
After two decisive campaigns in 1422 and 1423, Adai Khan lost all of the territory gained in the past and in 1430, the third Oirat victory wiped out his major strength, after which he could no longer mount any effective offensives and was forced on the defensive. Both sides attempted to utilize the stalemate to prepare for the next stage but Adai Khan could not recover from the previous loss. The Oirats soon launched another round of offensives and in the fourth decisive Oirat victory in 1434, Adai Khan’s major advisors, Arughtai and others, were killed. Adai Khan’s downfall was certain.
Death
In 1438, Adai Khan was defeated in Ejene when his territory was overran by the Oirats and their allies. Adai sought refuge in the Eight White Tents of Genghis Khan, however, being unarmed, he was murdered by Togoon taishi of the Oirat.
