The Part 3 information for the Frost artifact unlocks at AK5, and it talks about Captain Falric's experiences alongside Arthas. Falric is also found in Halls of Reflection, where we find *DING DING DING* Frostmourne. Perhaps now w/ AK5, Halls of Reflection will have something for us. OMW there now.
**EDIT** Didn't find anything. Will keep looking.