Cocky And Rich.

Another demon king said, "Yes we are in luck. But odds are that he is probably stronger now too."

"Even so, wealth awaits us."

The hellhound demon king said to them, "You're very lucky that I followed you now. Your little get-up wouldn't be able to take him on." 

The increase in the defense of the plane is minimal compared to the increase in the power of Aeternus. He should be as powerful as a level 6 demon king normally but the reinforcement makes him as powerful as a level 7 demon king within his plane. That means that had the hellhound not been here, then they would have returned empty-handed, or worse, they would have died. 

"Who will do the honor of gaining us entry?" The hellhound demon king asked the other four demon kings.