The darkness weighed onto Jola and he used his immense sword aura to fight back. This building was essentially a modified magic tower. Even though it was not as powerful as the magic chariot, there were dozens of magic arrays inscribed on it and it was pretty powerful itself.
If the mages in this building were to fight in the normal way, just a few of them would be able to cause massive destruction to Bifano's army. Lex's mages could not control every area.
The mages were hiding inside and commanding the stone statue ghosts to attack. The strongest few grade-4 mages were hiding inside the darkness screen and defending to the end.
Within the level-7 darkness screen, these grade-4 mages could not release any magic themselves and could only control the magic array to continue the attack. The darkness screen could not kill their enemies, they could only watch as their enemies killed them.