Thanks to the seniors of the Battle Arena Committee, Vale learned plenty of things about the Fear Stream and Spectral Hands.
After all, these students were the ones always officiating the duels in the arena and had seen plenty of battles.
According to them, the Spectral Hand mostly relies upon its speed to suppress or even kill its targets.
Furthermore, depending on the caster, this Spectral Hand can be extremely hot which could burn a person, or extremely cold which can freeze the target.
Of course, it can only be done if the caster's mastery of the spell is already at a higher level…
As soon as Vale saw Wilfred's lone Spectral Hand, he can already tell that it was using a burning aura that may scorch him if it gets closer.
Furthermore, it was followed by a wave of energy and Vale guessed that it was the Fear Stream that could make him an idiot if he was hit.