Here's my walkthrough updated to 100% completion of the hold, killing the Gentryii, to show that this can even be done without taking anything from Level 1.
I've also done a playthrough of the ATK route (using Level 1) in which I've tried to optimise to the best of my ability. I didn't finish that far behind Midootje; my final stats are 31347 HP, 2115 ATK, 165 DEF (Gentryii does 22776 damage with the invisibility potion). It's interesting that it's possible to kill the Gentryii with only one potion, and tempting to add an extra bonus boss to reward completion of that challenge, but... I'll probably leave it as it is
I've written a walkthrough for the ATK-route playthrough, but I won't make it publicly available. If any of the HAs would like to see it, just let me know.
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I thought of adding, as an ultimate bonus boss, an Adder with x22 stats, and replayed the last part of the hold with this in mind, aiming for just over the 2013 ATK threshold. I was able to get 75,000 HP, exhausting every resource available in the hold; but the Adder would take 78,000 with both potions and the Wyrmsmiter. Midootje would probably have succeeded.
In any case, I found this level of exact optimisation to be not particularly fun, and I don't want it to be required for a score checkpoint. Instead, I'll make the challenge to be killing the Gentryii with
neither potion, which isn't so exact (at over 1992 ATK, the Gentryii does 60,800 damage, and further ATK thresholds are reachable). There won't be a score checkpoint for this; I'll just add some extra dialogue.
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50th Skywatcher