Five minutes had passed since the players had entered the city; after only five minutes, that was the time it took for the nearly two thousand players to get into the sewer, the descent of the main enemy horde would still need at least 15 more minutes to reach them or at least realize they had been tricked.
Although the Zinders' magic was powerful, what surprised Ikky the most was the use of a strange energy that was also a shield that reinforced the curved edge of their swords. It was not worrying, but it was an uncomfortable factor because he could not really foresee how it would work.
The entire city was permeated with a strong temporal and spatial mana, I suppose derived from the forced exile of the entire area. Using bullet time was the easiest and most convenient option to face the large groups of enemies.