Question re: monster drops

[Ingwe Ingweron]

In watching Fizzix's "Let's Play Angband" videos, I noticed he knew when monster groups would start having a chance at object/treasure drops. It seemed like they needed to be some number of levels below their native depth.

Is that correct? And, if so, what is the general rule about when drops start?

I just saw a group of out-of-depth Barrow Wights and thought, "Oh, good, I should get some drops from them!" I took some risks and attacked, but not a single drop.

[Derakon]

The item level a monster will drop is max(monster level, average(monster level, dungeon level)). In other words, if the monster is out-of-depth (i.e. normally shows up deeper), then items will be dropped as if at the monster's normal level. However, if the monster is weak for its depth (i.e. normally shows up shallower), then items will be dropped as if at the average of the monster's level and the current dungeon level.

[krazyhades]

But whether or not a monster has 0 or 1 or 7 chances to drop an item is determined by the monster itself. A grey mold will never drop an item, but my understanding is that if a monster with at least one drop chance is encountered below native depth, then it is more likely that its drop chance(s) (indicated my "may carry up to..." in the monster memory, if you've learned it) will decide to create an item rather than nothing.

edit: A deeper monster is more likely to drop good items, where the worst possible item is "nothing," but the number of chances it gets to generate an item is based on the monster itself.