This is a pass-along plant that was called "Devil's Castle" by the dear lady who shared it with me. I haven't been able to find anything with that common name.
It has the square stem and saw-tooth leaves like Physostegia, but it has distinctive dark purple/black vertical stripes all along the stems. It hasn't bloomed yet, so I can't share any details of its blooms. It's about 2 1/2 feet tall. Any ideas?
LOL thanks Go_vols I guess I'll have to answer now.
Well Physostegia is sometimes grown here but its not often seen so I cannot give you a confident YES. The square stem certainly puts in in the mint family. The stripe may be a natural variation/mutation and I am aware that some people collect these curiosities, it would be interesting to see if the offspring carry on this trait.