What am I looking at and how shall i fix it?

What am I looking at and how shall i fix it?

What am I looking at and how shall i fix it?

I'm going to decorate the hallway. The hallway was a bolt on to the main house. The main house is made from timber frame and lime render. The hallway is brick. The wall in the pictures is solid and about 1ft thick.
What am I looking at? rising damp? Dry rot?
What can i do to resolve it? dig it out and plaster?
What about refilling it? should i use lime plaster or can i use gypsum?

Same image with flash:

by frustin

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