There is no Potion of Strength in boss depths and depth 21: that explains the generation variability, as a potion can be internally generated (decreasing the overall 9 potions counter) but won’t be dropped in those depths,
1 potion max per floor,
stage 1: 2 potions,
stages 2 to 4: 1 (40 %) or 2 (60 %) potions,
stage 5 : 0 (40 %) or 1 (60 %) potion.
So, in the whole dungeon, you will find 5 to 9 Potions of Strength, with a 12.96 % probability to find them all.
While I’m speaking of it, here’s the same thing for Scrolls of Upgrade:
There is no Scroll of Upgrade in boss depths and depth 21: that explains the generation variability, as a scroll can be internally generated (decreasing the overall 13 scrolls counter) but won’t be dropped in those depths,
1 scroll max per floor,
stages 1 to 4: 2 (60 %) or 3 (40 %) scrolls,
stage 5: 0 (40 %) or 1 (60 %) scroll.
So, in the whole dungeon, you will find 8 to 13 Scrolls of Upgrade, with a 1.536 % probability to find them all.
At depth 21 (the shop level) the quota jumps into the next bracket so the scroll that didn't get generated doesn't need to be generated immediately
The other two scrolls spawn on depths 22 to 24
Of course, the only reason that you would get an extra scroll in the demon halls is because you "lost" one from the city so it's not at all helpful. (Personally I feel this is a bit of a flaw and the SOU quota should be like the POS quota in that items must generate before the boss level)
Right, it’s indeed possible since v1.6.4 (only for SoU, not for PoS), i.e. since 2014/04/05.
Of all testimonies about “2 SoU in DH” have been given after that date, we now have a logical explanation! =)
I started the Prison with no Scroll of Upgrade, so it was easy to count. And I just found 4 scrolls of Upgrade in the Prison, one at each depth. Is it possible???
Notice that I killed Goo two times with the ankh's trick, I don't know if it can have influence. I also had a long pause after Goo, playing a lot of other runs with other characters. (Lastly, I used two beacons in this runs, but I guess there is no impact?...)