The monsters flooded Raagu's arrays in such numbers that the mana that was supposed to last minutes was quickly drained in order to kill them before they escaped the magical circle's boundaries.
Unlike the Lich King, Raagu had come prepared for the fight. Yet even with many arrays at the ready forming a wide trench of light between her and the enemies, only a fraction of them were forced to step into the magical formations.
The rest of them just ran around the arrays since not even someone as skilled as Raagu could cover a battlefront that extended as far as her enhanced eye could see.
She had killed hundreds of monsters in the first seconds of the conflict and kept killing more, but the Black Tide swallowed her light without suffering significant losses.