The Phoenix Ascent

Set in the Fifth Column universe though long before the events involving Sophia and team.
"One man versus an army. Can a rogue alchemist turn the tides of war? The Mongol army is storming China, devastating everything in its path. Their mission: recovery of an artifact with otherworldly powers. Their General will stop at nothing to recover it. Zhu is an alchemist in the wrong place at the right time. He has the artifact ... and an assassin’s blade at his throat. And he’s the only person who can beat them."