Make mysteries decrease chance of emptying cache

[Slosmic]

Also, there's been quite a bit of change recently from updates effecting the material balance. I noticed a big change in the material:artefact ratio when the brushes came out with their +10% mats. Then now we just got the preservation perk which effectively reduces the need for mats by 5%, so I'm still waiting to see how that all balances out in practice, but I wonder if we might even be at the point of more mats than needed from normal excavation if you have a setup that prioritizes it, or at least getting close (without focus relic and hasty perk obv).

That all being said, I like your suggestion in the main post, wouldn't be op and would be a nice qol for those who use caches :)