The Plan
Even before Ben explained to him the road to an imperial defeat, Leo already understood how to achieve complete victory and had been plotting with ChaosBringer on how to achieve it.
For Leo, the road to a complete victory was simple.
He needed to infiltrate the StrongHaven castle and kill every single one of the royal family members present there, down to the last Evanus child within.
Since the North Duke was there too, he had to kill him as well, and the whole Empire needed to know that it was him who did it.
Just like Ben before him, Leo intended to take on the role of a kingslayer, and become notorious throughout the realm for his strength.
Of-course, he wasn't a fool and did not genuinely believe that he could just waltz into the imperial castle alone and slay everyone in there without a worry, as he knew that it wasn't as easy as that.