The elusive Skull Lantern: as in why the guaranteed drop is not as guaranteed as it might seem
Recently on the topic of skull lanters, the topic of them being a guaranteed drop came up again. However, I've had recent playthroughs where I did not receive the guaranteed drop after killing all necromancers - despite the fact that it should happen - and doing a quick search I've found many other posts claiming the same. In order to figure out why it looks like that guaranteed drop is not as guaranteed as it should be (and in order to prove to myself that I'm not actually crazy), I've taken upon myself to investigate this strange anomaly.
Short background, the skull lantern is supposed to have a cumulative drop chance where it has a higher chance to be dropped with each necromancer killed (credit to the original investigation for the drop mechanics to Illusory Wall: https://www.reddit.com/r/darksouls/comments/17lje7s/correction\_on\_the\_skull\_lantern\_drop\_rate\_from/)
My first idea was check if there's a bug or a situation where the counter for the cumulative drop rate would reset after dying, reloading the area or closing/quitting the game. However, even before I've got to look into that hypothesis, I believe I've found out the reason, which turned out to be much simpler.
Once you head out in the alcove with the skeletons and the exploding skulls before the first bridge switch, Necromancer #3 is programmed to slowly walk forward onto the bridge, then once he sees you, should start shooting fireballs from his lantern at you. The problem is? The bridge is not in the right position. That means that unless he sees you before he falls, or you move the bridge in time before he reaches it, he keeps walking forward - until he falls to his death, as shown in the video above.
This behavior is so consistent that once I've noticed it, I was able to recreate it 100% of the time simply by rushing past towards the switch, then waiting there without turning the bridge - which can easily happen if a player rushes in then gets busy fighting all the skeletons that spawn there.
And if you're unlucky enough that this necromancer then drops the skull lantern (which will disappear unless you go down to the skeleton wheels without dying or reloading the area), then the cumulative drop chance resets, and now killing the sixth necromancer no longer guarantees the skull lantern.
TL;DR: Even though it's guaranteed to get a skull lantern on the sixth necromancer if you haven't gotten one before, there's a specific suicidal necromancer that can screw you over if you have bad RNG.