Favorite secondary skill.

I have Diplomacy. It's especially useful on generated maps where there are many powerful units of different levels guarding artifacts. By the third month with this skill, you can create a truly devastating army that will overwhelm any enemy without significant losses.

In my opinion, playing against the AI with Diplomacy is not interesting at all, it's just not interesting. I prefer to develop my own army - castles, external dwellings. But "Logistics" is just a MEGA AMAZING skill. "Pathfinding" on levels two or three, where there are no wings or dimension doors. ;)