I just want to make sure that I understand what is going on for this chapter, especially one what is Otto's actual plan. I'll throw all of it within spoilers but if anyone has any other points, please let me know.
After experiencing the Herrscher of Domination and their little pocket dimension to get to the Imaginary Tree
He declares his retirement and that he will give the position to Theresa in order to lure their group over in order to really get the void powers from Kiana in that location
After getting core of the HoDom by placing it in a clone of himself, he drains the power, he is now able to make full use of their pocket dimension go to the Imaginary Tree
He banishes Durandal to the land of the Kaslanas where their stigma placed in the PE is the strongest. This, I don't think has alot to deal with his plan to revive or save Kallen, just so she knows about her past before he is about to die.
I realize that Theresa uses the power of binding to stop Otto from turning back that one little section to when Kallen was killed, but I'm not sure that was his main objective, he seems to me to be the evil genius trope and something as obvious as the Oath of Judah shouldn't have been forgotten.
After Durandal escaped the "prison", she and Kiana team up to fight Otto. Who has gone to the Imaginary Tree already and become some sort of drone to the will of the tree.
At this point, he can't save Kallen because he is bound to it's will rather than what Otto wants to actually do
When Kiana uses her void powers on Otto and the spear is driven through from Durandal, the will of the Imaginary Tree was severed and he was now able to change history, and even though he is now "dead" (ha!), he was able to set one timeline where Kallan actually lived.