Bookwyrm burns Electrum to help navigate the swarm of monsters. He hits as many of them on the head as he can, using Pewter to enhance his abilities, and tries to make his way to the other side of the room.
Making use of the fact that they're retreating, he presses his attack until he reaches the door on the other side. By that point, all of the creatures are gone, except for the unconscious ones left in the room.
"We did it!"