Keiko
Spectating her master's battles with the Zayama Mage had allowed Keiko to understand its capabilities, albeit at the cost of Haruna having to sustain a few surprise injuries that were promptly healed away later. For one, the Zayama Mage had three main offensive tools at its disposal.
Those were a type of wind-based weapon it could produce, and a bolt of lightning that it could launch. As for its defensive capabilities, it could produce the same wind-based wall that the Zayama Warrior made on the first floor, and it could teleport. Although these tools may have initially seemed like a small amount to Keiko, there were two things that made them feel downright oppressive.
Firstly, their seemingly low mana costs, with each ability only costing 10 and 15 mana, and second, their short one-word incantations. It allowed the Zayama Mage to spam its abilities a way regular mages simply couldn't do.