Eredman, as a magician, though not suited to become a Tactical Level Magician, did not have a poor aptitude for magic.
With a fourth-grade aptitude in Transmutation and Manipulation, and a first-grade aptitude in Interference and Construction, Eredman's magic aptitude could be considered quite exceptional, just a step shy from that of a Tactical Level Magician.
Although this step was as vast as the heavens and insurmountable no matter what, with fourth-grade aptitudes in Transmutation and Manipulation, Eredman could still be said to be sailing smoothly on the path of a magician.
Therefore, at the start of the duel, Eredman immediately took actions that could be described as exemplary.
First, he chanted the fastest magic defense spell he could, raising a barrier.
In a duel between magicians, erecting a magic defense barrier is the first action anyone would think to take, allowing oneself to withstand the opponent's magic attacks while also buying time to chant other spells.