The Valley of Death (VoD) is found through the Grave Yard, NE from the Market Place.
I would suggest that a Lt Col on Ishies would be at high risk of a short life expectancy.
You can get one of the Arch Quest items in the VoD. There are Elete Skeletons in there and they are not called Elite for nothing.
You can also go through the VoD to gain access to the Holding Cells on route to the Prison Cells. They are even harder.
If you want to explore the VoD then I suggest you get a partner you can group with to assist you.