Where to find the serpent key?

I'm almost done with this confusing quest

[gaunty]

please be give more detail in your question.

is this the key that kol gives you or what?

It's the key used to open the serpent holds

You get the Serpent Key from Kreug The Wizard...here are some tips...have the guy who talks to Kreug be one who has no gold...When Kreug asks you if you are going to join their sect, say yes...he'll ask for a donation of 1000 GP...say you will pay it... "Why brother! You don't seem to have enough gold! I know times are difficult, perhaps if I let it slide this time"...he gives you the key...when you are done getting the Serpant statue, give him the key back and the doors to the rest of the Temple will open and the priests will all be nice to you.
The Dowry Priest however will only let you get away with not making your donation once (same as above, have a guy with no gold talk to him when he asks). After that, unless you pay (50 GP's if I remember right) he tells everyone that you are unworthy & to prepare you for the sacrifice! That's when you will have to kill everyone you see in order to stay alive.
I was able to cruise the Temple for quite some time and empty most chests and get most of the statues before I was labeled umworthy.
The Torturer's will always slap you around, no matter what your status is with the rest of the Temple's occupants but you can kill them with no retribution. However, The Inquisitor is in front of a door with a dowry priest inside and if you ignore him while you are offing the Inquisitor, you are labeled unworthy & everyone is your enemy. ; )

Well I killed Kreug (after I talked to him) before all the chaos started. I'm not certain where the key is, nor do I remember even picking one up after he was dead. If I can remember where exactly he was, I could probably use spirit eye to find it possibly?

I would think it should be where you killed him...I played it twice & the first time he would not take the key back so I killed him & the doors opened but that game ended with a system crash & when I started again the second time, he took it back.
Where you met & killed him was a room with a table & chair and four passages leading away from it...one of those passages is the long one you came up to meet him, where you had to pass the Serpent holds coming in the back door...another passage (straight across from that one) leads to the Serpent Incense Dispenser Thingie...I don't remember exactly the descriptions of the other two passages away from that room but at least one had a stairway in it. I hope this helps you somewhat!