I have no idea either – it’s available for Fate if you sell your soul, but only at Hallowmas, not all year round.
So, about expedition data – I only have scraps of notes from myself and friends about highest and lowest values, so I could do the survey and provide a couple data-points if it’s helpful, but it might throw off the overall statistical curve. Still, it seems like bundles and treasures follow a straight-line random formula so maybe just knowing the ranges is all you really need. That’s what I based my numbers on: assumptions about low/high values and how the Storynexus Rich Effect was set up. If it’s not actually a straight line, it’s doing a very good impression of one!
[quote=Cecil ]The Temple of Uttermost Wind’s Unpredictable Treasure goes down to a value of at least 54, which means there’s either a 7% or 9% chance of ‘A wooden mask?’ + others, and twice that for Airag (depending on whether the UT value goes all the way down to 1 or not)
The Gallery of Serpents has equal chances of Airag and Tears, both 25% each.[/quote]
I have lowest observed Uttermost Wind value as 41, which means a 9.5% chance of wooden mask. (Was rounding up instead of being precise, sorry.)
Airag values seem to go from 120-139 (avaiable even in non-fate expeditions, right) and 160-179. Gallery lowest value I’ve got as 161, which fits a hypothesis that someone set these to be [die roll]+[fixed value] and fixed value was a round number (in this case [d:80]+160, to use storynexus syntax). But 160 is available for non-fate-locked too, and from data on non-fate expeditions seems to be the very tip of "a carefully wrapped container." The ranges for rewards seem to start at round numbers, but the die rolls + round numbers make the setting of "Uncovering an Unpredictable Treasure" (and bundles too) start at 41, 161, etc. It throws data off in funny ways!
Airag (161-179) is thus slightly less likely in Serpent than the other rewards, and Tears, which I got at 220, runs from 220-240 so it’s slightly more common. The latter, at least, fits the arc of your data!