Darius hadn't broken his promise. That very night, Sejanus and the other captured Astartes boarded a Medivac and were safely taken to one of the two Imperial ships from Terra in orbit. As soon as they were aboard, they eagerly left Canopy Star's orbit and headed at full speed out of the Taiwei system.
Over the next few days, just as Darius had expected, Horus began contacting him frequently to hold secret talks that no outsiders knew about. The other man even made a secret trip aboard a ship to an outer orbit of Canopy Star, then personally met with a newly created female Astartes aboard the Noxus.
After that, he began making concessions in the negotiations and even proposed a series of conditions for an exchange.
Unfortunately, Darius didn't accept.
He simply kept the other man waiting, taking the opportunity to make a series of reasonable and unreasonable demands, some of them downright excessive.
For example, he demanded that the other man withdraw from Canopy Star, among other things.
Then, while the negotiations favored them and the other side was deliberately holding back, Darius launched several large-scale raids and battles right under their noses. In one fell swoop, he suppressed several openly rebellious cities and strongholds, including those held by the planet's native XVI Legion, and brazenly laid Canopy Star's problems bare before the other side.
The result surprised Darius and the base's staff officers, though it also seemed only natural: the other side turned a blind eye to what was happening and, in the negotiations, continued to focus solely on obtaining Mulan, who had already been transformed into an Astartes Space Marine. They even stopped making an issue of Canopy Star and the Taiwei system.
Seeing how much the other side cared about her, Darius and the others