The succubus queen wouldn't have minded if all the hellhound demon king did was tag along. No one will say no to free help. Especially when the help is level 7. But demons don't do things in moderation. The hellhound demon king took over the group and became its leader by force.
The group that she formed contained four demon kings including her. All of them are level 5 demon kings. The succubus queen would have very much liked to keep it that way. She intended to put together 5 demon kings with level 5 Authority. That way, she will be the leader and she will be able to take the bulk of the wealth. She was to take 30% while the rest took 17.5%. But the presence of a level 7 changed that.
Having a level 7 among them has granted them confidence but she doesn't think it was worth it. She doesn't think that they didn't need the boost in confidence or the power of a level 7 demon king. Five level 5 demon kings are already more than enough to pressure the Reaper into giving up his wealth. They will barge in forcefully into his plane and threaten him with violence. They will also swear an oath to leave him alone and not kill him after he has surrendered most of his wealth.
The use of only violence will not make a demon king give up their wealth. They have to be given a way out or they will get desperate and resort to extreme measures. The succubus queen had everything all planned out. 5 is also the right number that ensures that one of them will die if they fight the Reaper. The reaper might want to test his chances first knowing that they won't kill him without getting his wealth. So it is probable that they would have fought if 5 of them had shown up.
If they are 6, the reaper will give up directly without a fight. If they are 4, the reaper can take out one of them with his black beam which will leave 3. He has a much higher chance of success against 3 enemies. But if they are 5 and the reaper manages to kill 1 of them. 4 is still a good number to subdue him quickly. That means there will be more loot for the remaining four.
All of that won't happen anymore now. The reaper will capitulate as soon as he sees five of them with a level 7 demon king. He is reasonable enough to realize that he stands no chance at all. Then she will take just 15% of his wealth. She can't complain though. She isn't strong enough to ask for more and 15% of Aeternus's total wealth is bound to be a lot too.
If she does complain, it is certain that she will be on her own in that regard. The others surely won't agree with her. The presence of the level 7 demon king has only reduced their percentage of the loot from 17.5% to 15%. That's a worthy trade for the extra power. The one that suffers the most because of the addition of the demon king is her. Her initial pay of 30% got slashed in half.
She couldn't prevent the hellhound demon king from joining her group but she took some precautions. She has to be afraid of the hellhound for the very same reason that the Reaper will be afraid of the hellhound. The Hellhound is stronger than her and she can't trust her leader not to capture her to force her to give up her own wealth after they robbed the Reaper.
They only made an Oath not to act against each other until the loot has been secured unless their lives are in danger. Anything can happen after the heist. So she made sure to inform someone of her general plans so that someone would look for her in case she disappeared.
She didn't just stop at making plans in case of betrayal. She also made sure to complain and grumble about their indefatigable leader while she searched for the Reaper's plane. It took a few hours before they found his plane. All five of them gathered at the tributary leading into his plane.
The golden crowns on their heads made them stand out amidst the dark purple water. The light from their crowns showed their relaxed features. The battle is nearly upon them but they are still not nervous or anxious. They took turns to check out the energy signature and confirmed that it is the Reaper's. The bubble that represents his plane is covered by a dark film of corrosive energy that the Reaper is known for.
"So this is the plane. It looks reinforced and stronger than normal. Did he use the Authority of a Celestial Supreme to reinforce his plane? What a waste of resources." The hellhound demon king grumbled unhappily.
The Reaper's plane looks very strong and sturdy. It is not normal at all. Planes should not have external defenses. Their true power is realized when you are within their boundary instead of when you are outside. So the absurd defense of the Reaper's plane is odd. But there is an explanation for it.
Some demon kings use the Authority of the Celestial Supreme to strengthen their plane. It will make it very difficult to forcefully barge into and it will also make the demon king extra strong in their plane. It has no other benefits though so it is considered a waste of good resources.
It is much better to absorb the Authority of the Celestial Supreme to gain a level or exchange it with demon gods for other things. She knows a demon god that is very open to deals and will be very happy to get a Celestial Authority.
One of the demon kings said in excitement, "The Reaper must be very rich. He has to if he strengthened his plane to this level. We are in luck."