With the help of Tasty Onions, I've been able to do a little farming of Soul Material. Even with Drop Rate up 5, it doesn't seem to drop much. Perhaps as little as from 2-5% of kills. it does however seem heavily weighted towards when you have recently died, with about half the monsters dropping it.
Results of mapping: (c=Chaos, L=Lawful, R=Reincarnation)
7c, 12c, 9r, 12c, 9r
Coming from a mixture of living dead, zombies and beetles (Not sure which ones)
Decided that higher level dungeons drop more, so visted...
21r, 21r, 22c, 15c, 22L, 21c, 17L, 15L, 19L, 16L, 20r -> 19 ± 3 per drop
First 2 came from a hydra plant and a beetle, the remainder came from Black Flies.
I noticed that after an initial high drop rate, the rate recreased to almost nothing, and then increased again, to the extenet that it was dropping from about 25% of monsters... as far as I could make out. It's hard to tell how many are being killed when you can't see any. It might average out to 10%, assuming it's a nice number.
For completeness, we moved onto...
19L, 17r, 19c, 16c, 15r
first 4 from beetles, 5th from a death carrier. Drop rate seemed quite low. Next up,
25L, 28L, 23r,
All from Zule warriors. Nothing much dropping. Moved onto
25rK, 26cK, 25rK, 23LK, 26cK, 27cK, 29rK, 31LK, 29cK -> 26.5 ± 2.5 per drop | Low drop rate from kobolds.
I also farmed Zombies, and ended with so many results that I'm not going to put them here for lack of space. In half an hour, I got more than 1250 soul material all up, in 37 drops. The range, based off 40 drops, is 34 ± 6 per drop. Since there was a large deviation I suspect that each of the two types drop different amounts. Regardless, this is an incredible place to farm for soul material!
Aria Reservoir (i=Insect)
...More to come