I've started scratching my head about faction power. I was playing my last Legendary Heroes game with Altar. For the longest time my faction power rating was 1st or 2nd, Magnar being a few points behind or ahead from time to time until we reached a score of ~185 each, with Resoln and Gilden being quite a way behind.
Suddenly out of the blue Magnar's faction power jumped to something like 2700. WTF moment. I decided at this point I had to take him down a peg or two, so I built some armies for 2 more of my heroes (other than my one champion stack) and went on a rampage across Magnar lands, effortlessly capturing or razing his cities.
Some 2 hours of game time later my faction power is 560, and Magnar's is 50. I have reached the end of the tech-tree by this stage, and built several of the towers for the master ending. This may, or may not have boosted my rating. So may the cities I conquered and held. Yet on one or two occasions when I conquered a town, I saw no change. I haven't kept my eye on the power-meter throughout, you can tell ...
But WHAT was that 2000+ jump in faction power all about? And where have those power points gone? I'd really like to get a handle on this, since the rating clearly has an influence on diplomacy, yet how to manage this rating is shrouded in mystery.