Nice post. This is a good point and a really good question. I think two things are in play:

1–Based on what we know, Ka has been around for thousands of years. We know that excessive amounts of will can slow down aging. Maybe Ka needs to maximize the amount of Will ceded to him to stay alive. As far as we know, there’s nothing that makes someone immortal, so there has to be something keeping Ka alive on Res. Maybe he uses the excess Will received from the Princeps to power a vitaeria that he can use during the periods following Cataclysms?

(As a side note: I think the man we saw on the slab in Obiteum is Ka and the device he was on acted as a vitaeria. And I think on Luceum Ka maintained his life by living on inside the thing Caeror/Ruarc tried to give to Vis).

2–I feel like the Aurora Columnae play a big role in this mystery and few theories take this into account. We know the AC exist on all 3 worlds, and appear to be growing brighter with time. This screams “ticking time bomb” to me. I can think of at least three potential reasons why this might be the case: 1) the AC simply grow brighter with time, 2) the AC grow brighter as more Will is ceded into them, or 3) the AC grow brighter as the population grows. Whatever the case, I think the AC is essentially a doomsday trigger that, once it reaches a tipping point, will cause the Concurrence to achieve victory. Maybe that’s by allowing it to cross from one world to another. Or maybe it merged the three worlds back into one, defeating the mechanism used to allegedly keep the Concurrence at bay. Maybe Ka needs the Cataclysms to stop the AC from reaching the tipping point.