simple area access question

So I have figured out that for the bounty The Blooddrinker I must access the Depraved Sanctuary all the way back in Act 1. After failing to get the iron door open, my “research” shows that I need a key for this, which can spawn from some cultists near that door. I have logged out and back on half a dozen times now, and am not getting a key drop. Is this normal, and just a random element? The wiki says it’s a “guaranteed drop” from hero cultist in the “basement to the south-east”, but I fail to find this basement. What am I missing?
thanks much!

You get a guaranteed key from quest, IF you choose to coop with traitor (Direni). If not, you wont get the key.
Key also drops from cult members in that area. Sadly, it seems that sometimes it just fail to drop, no matter how many cultists you kill. It happened with some of my chars.

Ah ok thanks. Then I just need to sort of reload and come back again and again…