1) It greatly strengthens all walls and buildings by increasing their armor approximately x5 vs. most weapons (a bit more against bows) and approximately x4 vs. siege weapons. This gives you time to get to a farm that is under attack and defend it, if the attacking group is not too large.
2) It slightly (+10%) increases the non-upgraded armor of most units. I felt that the armor upgrade was just too big an improvement, making it practically a necessity, especially against upgraded weapons. This is not going to make a huge difference, but it might help a bit.
3) It incorporates the Elven Guard mod by Steve Shepherd (AKA Gholin). In his readme, he said people could use his mod if they gave him credit, and I enjoyed it so much, I’ve done so here. His original readme is included in this zipfolder as well, so you can see what he contributed.