I would say it depends. If they treat magical nodes like "buildings" in the map editor then it may very well be just a simple "click" and change the name. Stardocks pretty good about stuff like that. You could rename practically anything in Gal Civ 2.
If not then Scoutdog is correct. Once you find the proper file and open it and find the string you could rename each one to "Fountain of Asskicking Goodness" if you wanted. Really anything will work here as long as the code doesn't have a pre-set limit on how long the name can be.
I don't think you quite understand how life and death magics work: there is no "node" that you ujse. The magic auto-accumulated using some as-of-yet-unknown formula that I
think is actually lumped in with the economic and city-growth systems. In short, it is actually part of the
game like, say, taxes, as opposed to a part of the map or character.