Who they were
Yang Guang, the second Sui emperor. Traditional accounts say he took the throne amid the suspicious death of his father, Emperor Wen. His posthumous name Yang (煬, “wastrel”) was assigned by the victorious Tang.
What they did
He built on an imperial scale: the Grand Canal was completed under him (605–610), Luoyang was rebuilt as an eastern capital, and the young examination system advanced — the jinshi degree is traditionally credited to his reign. Then came three disastrous invasions of Goguryeo in Korea (612–614), whose ruinous cost triggered revolts across the empire. He withdrew to Jiangdu (modern Yangzhou), where his own guards strangled him in 618.
Legacy
With Qin’s First Emperor, he became the archetype of grand projects and overreach destroying a short-lived dynasty — even as his canal fed China for centuries.