Before the jet of fire ended, Gadorf charged head first at Lith like a ram. Even with the flames still raging around him, fighting off the blinding pain with light fusion, Lith saw the wyvern coming at him and acted accordingly.
The heat had not only injured Lith, but also weakened his constraints. He could now let himself fall to the ground, holding the sword with both hands close to his chest. As he expected, Gadorf Blinked at the last second, keeping his momentum to strike at him from a dead angle.
It was what Lith would have done in his shoes.
With the back on the ground, however, he had no blind spots. The area was still shrouded in flames, Gadorf had no way to know Lith's exact position. His head only hit empty air, Lith rolled away as soon as the Blink happened.