In Murong Jiu's previous life, although news that the Xiongnu possessed secret weapons had reached the Capital City early on, people did not take it seriously.
Based on imagination alone, who could know that "Fire-thunder" would possess such terrifying power?
"Fire-thunder" might sound inconspicuous, but it is actually like an explosive pack. When ignited with a firestarter and thrown into the enemy crowd, it could kill or injure more than half of them instantly, with bodies being blown to pieces.
With "Fire-thunder" as their weapon, the Xiongnu could be said to be invincible. They also deliberately concealed it, using it only when they intended to leave no one alive.
Thus, people on the Great Yan side could only hear the explosion, but could not imagine the terrifying power it held.