Oh the old ones have smiled upon me. When I jumped onto the farmhouse I found that next door was the Demonologist Citadel.
http://www.dom3minions.com/~gandalf/CoE3/AAR2/turn38.JPG
There are no commanders there. Just 24 troops. Mostly archers, and a couple of swordsmen.
Now for some strategy. I will get back in the ocean and summon. Hopefully get enough to take the citadel. It has a high defensive ability though so I need to be sure. If I am lucky, maybe he will march out an army while I am waiting. That will leave it more vulnerable. There wont be any special things like demons.