These many souls were actually unexpected to Roy.
Xeron had been really reckless. Had Roy been leading the army, his first thought would have been to retreat right away when facing the powerful elven troops that were three to four times his numbers. But Xeron still wanted to try using magic to reverse the situation. Moreover, he had aimed the Meteor Shower at the densest place on the battlefield. Thanks to Xeron's magical help, Roy picked up a huge bargain.
The souls of demons usually could not remain in another world. After the demons died, the Ouroboros Mark would pull the demon souls back into the Abyss. As such, all the souls remaining on the battlefield were from the elves. Looking at the densely-packed souls, Roy estimated that there were over a thousand of them. Xeron's big move had likely damaged one-third of the elves' military strength.
