This is a high fantasy trilogy that I read in the early 90’s where the magic system had a very unique requirement that required a person that was sensitive to magic power, who would dedicate his life not to casting/making magic but only with the ability to absorb the magic power around him like a battery and then was able to give that power to an actual mage that could then use it to make magic. The mage would be useless without having access to this other person who would feed them magic power.
Also by the third book the magical world gets invaded by a world/reality that has modern technology like tanks and guns.