Jakra tried to emit a burst of blue Origin Flames from his body, but they came out barely bright cyan and Lith's Flames devoured them before moving onto his armor.
"I don't know which one of your creations performed this miracle, but you are not the only skilled Forgemaster in this room." Jakra had no idea that it was Solus draining the surrounding world energy to have weakened his Flames and enhanced Lith's.
He just assumed that it was the effect of one of his artifacts and activated the Kingslayer armor's barrier. Thrud was well aware of the powers of all Guardians' bloodlines and had made sure that her spouse had the tools to counter them.
In the case of Origin Flames, they didn't discriminate between caster or foe, they would eat at everything they met. Hence a powerful barrier that sprung out with enough speed would produce a shockwave that would send them back against their master.