This is what I think would have happened or could have happened if DomDaniel had died when Alther had pushed/he fell off the Wizard Tower.

A Darke spell is caste upon Marcia, making her powers slowly leave. Septimus is able to help her, but severely burns his hands and arms in the process of doing the spell to reverse Marcia's Darke spell. Marcia blames herself for his burns, and things just go downhill.

Some stuff about Marcia after Fyre. I may also do some things with her after PathFInder as well but I'm not sure yet.