Vesper, the blood necromancer

Back to the Stormwach tower: 

"Bloodbound Legions, arise," Vesper uttered, and immediately, the dead porter soldiers began rising from the dead. He wasn't one to care about morality, but Rasoul cautioned him not to turn the dead of their allies into his undead soldiers. He only went for the dead of the enemies.

Vesper doesn't care about whom he turns into his undead or how he acquires them because he knows that in war, morality is not considered a primary factor. It's kill or be killed, and he isn't one to stand idle and be killed.

As more and more soldiers started rising from the dead, the Sundance soldiers continued to make their retreat. Ragnar stepped in to ensure all of them made it safely to the Citadel. With General Allistair frozen and lifeless, the entire Porter army became disorganized. The other generals tried to regain control, but before they could make any progress, Vesper spoke again, "Bloodborne Bombs."