I have a hard drive which had it's partition deleted, fdisked, in windows 10. Contained on the drive's partition were multiple MRIMG files from backups performed in the past. They are quite large, almost 5-TB in size total.

I am attempting to use 3rd party recovery tools to restore the partition (without success) and am now in 'deeps scan' recovery mode attempting to find the .mrimg files without success. Any advice or recommendations on how to recover these files of images of my system?

Thanks!
MS52538

Or for that matter, does has anyone ever tried to recover .mrimg files from a deleted partition, with success - or know if you cannot?

I've never done it and unfortunately I don't know exactly what was modified on your HD when you did the partition delete and whatever might have followed the actual deletion. If the partition table  gets its addresses adjusted then there is a big problem because nothing will make sense when looking at the modified partition..

If you can recover the image files they have to be bit perfect or they will not restore as an image. Depending on what and where the "bad bits" are you may be able to mount and recover specific files from within an image.

Over the years with various imaging programs I can recall people trying to undelete an image file but I don't remember a partition deletion issue.