Runmust Singh was a sworn member of the Black Company by the time of Sleepy's leadership of the group when it was underground in Taglios. He and his brother Iqbal, who was slightly smaller, were key Company operatives during both Water Sleeps and Soldiers Live.
The two brothers were imposing, hirsute men of the Shadar race and religion. They shared one of the most common Shadar surnames in overpopulated Taglios, and were completely unrelated to Narayan Singh, one of the Company's most notorious archenemies.
Runmust and his brother Iqbal were veterans of the Kiaulune wars which preceded Water Sleeps. They were from the southern continent but their particular origin was not specified (they were most likely Taglians, but, may have also been Jaicuri, Shadowlanders, or some another race). Like all members of the underground Company at the start of Water Sleeps, the Singhs worked diligently at a day job, and handled Company affairs during off-hours. Their job was unspecified but, like Slink, they might have been laborers for Banh Do Trang, their Nyueng Bao collaborator whose warehouse was the Company's secret headquarters.
Runmust's first major action described in Sleepy's Annals was when he and Iqbal threw a thug hired by Chandra Gokhale for "the long swim downriver" into the great river. The thug had been sent to spy on Tobo. Shortly afterward, Runmust and Kendo Cutter abducted Gokhale.
Runmust was among the first Company group which departed Taglios, led personally by Sleepy (the Annalist and ranking officer), the day Banh Do Trang died. In addition to Sleepy and Runmust were: Iqbal and his wife Suruvhija Singh and their three children; another Company veteran named Riverwalker; two key allies (Uncle Doj and Ky Gota); and three valuable prisoners (Narayan Singh, Willow Swan, and the Radisha Drah).
Now on the road toward the shadowgate, they were north of the Grove of Doom when they were suddenly faced with Mogaba and his Third Territorial, heading in the opposite direction. The haggard-looking Company group passed by, unnoticed by Mogaba and his professional soldiers... except apparently for Mogaba's black stallion, which recognized its former rider, Sleepy. Inside the Grove of Doom, Runmust was armed with one of the last remaining fireball projectors and kept close watch over Narayan Singh.
When Sleepy finally acquired the golden pickax from their cooperative captive Narayan Singh, Iqbal's oldest son Bhijar noticed something special in a deep crack on the artifact. Runmust was present when Iqbal used a knife to pry off a piece of the relic's outer shell of iron, revealing the solid gold beneath.
Runmust and his brother's whole family made the stressful journey south, through the shadowgate, across the lethal glittering plain, and into the bizarre fortress with no name. There, they saw the mysterious golem Shivetya, and later, Runmust was one of the first people to consume the food, called manna, which Shivetya supplied for the hungry group. He, along with Iqbal and Riverwalker, became giddy (the manna's side effect) and set off, singing, into the caverns below the fortress to find Sleepy and Willow. The 3 soldiers followed the smoke of the incinerated Books of the Dead to find Sleepy and Willow, and they fed the pair their first taste of Shivetya's manna.
The Company – now reconstituted with 8,000 well-trained recruits from Hsien – re-entered the homeworld in Soldiers Live. Somewhere north of the Plain of Charandaprash, Runmust and Iqbal led the group of Minh Bhu's younger rangers from Hsien which captured the Daughter of Night and Narayan Singh. They then fought the Protectorate garrison from Nijha. It was a bloodbath for the Protectorate forces. However, all but two of the Company's rangers suffered serious wounds, and the Daughter of Night was captured by the Taglians.
Runmust survived the bloody, costly Battle at the Shadowlander cemetery, but his brother Iqbal was among the many noteworthy fatalities of that fight. Subsequently, Runmust (following Shadar religious law) would be expected to take responsibility for looking after Suruvhija and her three children. On crutches, he led Croaker to speak with Sleepy after the battle. Later, at the Siege of Taglios, Sleepy and several of her closest officers were killed in Mogaba's mechanical trap at the city's South Gate. Croaker wrote that he suspected Runmust was among those fatalities, but since this is not confirmed later, Runmust's fate is unclear.