This addon is intended for people hunting down the old Naxxramas appearances. It will display the locations of all possible frozen runes on the map. This addon requires HandyNotes. While player coordinates don't work in dungeons, you can still see map POIs.
Frozen Runes are used in crafting Old Naxxramas gear.
This will not work in WoW Classic as there are no maps in instances. Don't.
There is no way of knowing if you've looted a frozen rune already and many of these are in fact actually capable of respawning.
If you find additional Frozen Rune locations, send a screenshot of the map location. I'm pretty sure I got them all but it's always possible I missed one.