Han Wu was a master weaponsmith in Liyue who lived around the time of the cataclysm five hundred years ago. He is most famous for developing the Prototype Series with fellow weaponsmith Yun Hui, as well some of the weapons in the Blackcliff Series.
After the cataclysm ended, monsters still ran rampant across Teyvat. To combat them, people turned towards supernatural arts, but found that the weapon production techniques were not up to par and broke easily. Realizing they had reached the limits of the individual skill, Han Wu and Yun Hui joined forces to develop the Prototype Series.
The two eventually started their own families. Wu's son, Han Ce, had no intention of taking up the family business, however, and became a wanderer who journeyed across Liyue. It was not until after a certain incident at the Chasm did father and son reconcile.
Realizing that the ores available to him were limiting his weapons' potential, Wu used one of Hui's connections to take a mining crew into the Chasm in search of crystallized blackcliff. However, a cave-in trapped them inside, completely cutting them off from the outside world. As his men fell to madness and despair, Wu found his prototype sword and used it to carve their way out of the mine. When his sword hit rock, it released a deafening roar — something that none of the survivors ever spoke about. Wu came out of the incident greatly changed. Upon hearing about it, Ce hurried home and found that his fiery-tempered father had drastically mellowed, and for the first time, the two were able to reconcile.
Several years later, a crisis fell upon Liyue: the Chasm was rocked by great earthquakes, forcing it to be shut down. Upon hearing about this, Wu was wracked with guilt, believing that he had disturbed the dragon that lay underneath it during the cave-in. He dragged himself out of his sickbed to forge Blackcliff Slasher, ordering Ce to build a shrine in the cave and place the sword in it to ward off evil and rebuke the dragon.
A few years after wards, Han Wu passed away peacefully in his sleep. That very same day, the shrine emerged out of the cave, the sword glowing as if grieving the death of its creator. Han Ce went to the shrine that night and retrieved the sword. He also found his father's weapon designs for the prototypes and with them, created the Blackcliff Pole. He decided afterwards to continue the family business.