"Oath Breakers, find and kill the Lieutenants. Both of you go together since they've got a level advantage and their defenders." Cain instructs the last two Legendary Demons he's not merged with.
They disappear instantly, and Cain hopes that their assassination skills will be enough to take care of the Lieutenants. If the big boss is here, he should have brought both of them unless he was arrogant enough to leave one behind at home to run the city in his absence.
If he organized this attack himself, he might have been gone a while arranging all the mercenaries, which would be great for them, with one fewer dangerous targets and a reduction in total summons.
Cain had just reached the west wall when a cheer went up in the East, lord enough that even over the roar of the Cannons, it carried across the castle. Hopefully, that was a sign that an important figure had been killed. There were a lot of attackers coming that way.