According to SimulationDescriptors_Mob.xml, both normal and elite Keepers have DustLootProbability set to 1, presumably to give 100% drop chance of dust.



I just killed a level 4 Keeper on floor 9 using hit-and-run attacks with the Pyro, and did not receive any dust for the kill. This happened on the current Steam version of the game. The Keeper burned to death while the Pyro was waiting next door. Even after entering the room to check for dust, there was still nothing to be found. My Pyro also had a Hand Vacuum equipped for +12% dust loot chance.

I think that each floor has its own Dust Loot Probability and that Mob Dust Loot Probability is then used to calculate based on the floor's. If that is how it works, then fighting a Keeper, say on Floor 7 Easy Mode which has a base probability of (random made up number) 70%. Then the 100% of the Keeper would translate into an actual 70% as opposed to a 50% mob which would result in a 35%.



But I haven't looked through the files lately and it is pure speculation on my part.

Thank you! I see the adjustment in SimulationDescriptors_Dungeon.xml now. It turns out floor 9 has a 0.36 multiplier on DustLootProbability, and there is likely another 0.75 multiplier due to difficulty level, so what I was seeing with the Pyro was nothing out of the ordinary. My experience was just biased by the fact that my two previous Keeper kills on the same floor with Skroig both yielded dust by chance.



I took a closer look at the Hand Vacuum too, and it seems like the Pickpocket bonus of +12% I had was being applied as a 1.12 multiplier. This makes the item nearly worthless on higher dungeon floors, so I must remember to sell it earlier on my next playthrough.