Gian was panicking.
He could have never thought that someone like Eren would bring him to his knees. Every time he thought that he had understood Eren's limits as a ranker, the guy would go ahead and surprise him.
The use of potion bombs came out of nowhere. He would have been a done deal if he hadn't deployed the defensive artifact he was wearing as his belt.
Gian knew that things had gotten serious when Eren managed to hurt the red lightning panther. The spirit beasts didn't have mortal shells. Their tamers would need to manifest mana bodies for their souls to reside in. The beast's soul would be called back to the caster's mana core, which would serve as its new home.
However, the spirit beasts processed the pain and other senses the same way when they were alive to some extent. Furthermore, their souls could be damaged by brutal attacks.