So, i was Blood specced until recently, when i respecced to a tri specc and got a permanent death rune.
Here's how i did it.
First thing i did was use an obliterate to get two death runes, one ice and one unholy. I then used the unholy Death rune and left the ice one. (Death Rune Mastery from the blood tree does that).
Secondly, i respecced 17/33/21.
Voila, perma death rune.
Ps. Make sure you use the unholy death rune, so you just have the icy one left. Else, it wont worked. Tested on an additional DK aswell.
noch ein paar "kleine" bilder ^^