book 3 climax Brainstorming (spoilers?) (Patreon)

Okay, so the dragon and Perry are pooling their knowledge and resources to create some mind-bendingly powerful magitech, then they're gonna kill each other over who gets to keep it.

That's the plan, But i don't have much mind-bendingly powerful magitech solidly in mind that could be the end-game for them.

so my question(s) is(are) this(these):

1: What kind of improvements to Perry's spell-storage could be made? What kind of spells could be invented? How would his Table of Essences work?

2: How does the secret book pilfered from his dragon mother's den, that general Abrams knows about (but but tyrannus doesn't) be used against the dragon in the finale? (chekov's gun)

3: How much time do you think should pass working together before they try to kill each other? What's the turning point? My first thought was when Perry gains a level and suddenly becomes significantly more powerful between one day and the next, and Tyrannus realizes he's on a shorter timer than he thought. my first thought was maybe six months to a couple years? Too much time skip? do we prefer none? Would you prefer to be present for baby time?

4: Did I forget any hanging plot threads that could be revisited at the climax of the story?

5: any other questions/ideas?

I'm trying my damnedest to write a smart villain, so I'm straining my brain, and need outside input to come up with more/smarter things than my limited, feeble monobrain can do.