Soulania Kingdom was thinking of using Castle Rock City as their cannon fodder in this war, and have them at the front for everything.
They were planing of entering the war only when both sides were too dilapitated to pose any threat and become the rulers.
Of course, they didn't expect everything to run through without spilling even a drop of blood but most certainly it wouldn't be to the point that they would have to suffer.
Tianlong Yun had the same plan as well though, he was never intending of using his peoples lives to take over this Soul Dimension, not when he had such a great ally by his side.
Both sides wanted to use the other to pave their way towards the rule, and only time would show who would be the one winning it all.
It would be useless to discuss more with this 2nd Prince though, as there was nothing to gain of him.