A man lies on his deathbed, the ruler of the largest empire in the Indian world. His ministers have locked him out of his own treasury. All he has left to give is half a myrobalan fruit, and he sends it to the monks. This is how the greatest emperor of the Mauryan dynasty ends his reign: not in conquest, but in a gesture of open hands.

He was born around 304 BCE, a prince whose own father reportedly despised his rough skin. When the emperor Bindusara needed rebellions suppressed and provinces governed, he sent young Ashoka away — to Takshashila in the northwest, to Ujjain in central India. Whether this was trust or exile hardly mattered. Ashoka proved himself capable in both.

His ascent to power was brutal. When Bindusara died, Ashoka seized the capital Pataliputra and, by most accounts, killed at least one brother, perhaps several, to clear his path. He was crowned emperor around 268 BCE, the third ruler of the Mauryan dynasty.

For years he ruled as Chandashoka, the fierce. Buddhist legends describe a torture prison he built in Pataliputra, pleasant on the outside, horrific within. Whether embellished or not, the portrait is of a man who held power through fear.

Then came Kalinga. Around 260 BCE, in his eighth regnal year, Ashoka invaded the Kalinga region on India's eastern coast. His own edict records what followed: a hundred thousand killed in battle, many times that number dead from the aftermath, and a hundred and fifty thousand taken captive. He had won. And it horrified him.

His Rock Edict Thirteen — carved into stone and distributed across the empire — is one of the most remarkable documents any ruler has ever produced. He writes that the conquest of Kalinga filled him with profound sorrow and regret. He would seek no more territory. Victory by dharma, righteous conduct, would be the only conquest he pursued from that point on.

What followed was a reign unlike almost any other in the ancient world. He planted trees and dug wells along roads. He built hospitals for people and animals alike. He abolished the death penalty. He sent edicts of religious tolerance carved on pillars averaging twelve to fifteen metres tall, dragged sometimes hundreds of kilometres to their sites. He told his subjects not to denigrate other faiths but to learn from them.

He sent Buddhist missionaries across Asia: his own son Mahinda to Sri Lanka, others to Kashmir, to the Himalayan regions, to the Greek kingdoms in the west. His Rock Edict Thirteen names Greek kings — Antiochus, Ptolemy, Antigonus among others — as recipients of his message of dhamma. Whether they listened is another matter; that he tried is inscribed in stone.

Ashoka died around 232 BCE, in his thirty-seventh regnal year. His empire fragmented within decades of his death, and the Brahmi script in which his edicts were written was forgotten for over a thousand years.

When scholars deciphered that script in the nineteenth century, Ashoka came back into history. The lion capital from one of his pillars became the emblem of the modern Republic of India. His wheel, the Ashoka Chakra, sits at the centre of the Indian national flag. A man who once built a prison called Hell left behind, as his lasting mark, a wheel of law.