It took me four tries on expert with Yithril, but I'm finally rolling now.

http://www.mediafire.com/?meud1j57pzpx8rj

Instead of one super sovereign, I decided I was going to need two!  So here is Verga and his twin brother Craul.  And there's really nothing special about these guys, but they had some good armies with them.  Verga had juggernauts and Craul had all the non-Juggernauts I managed to keep alive until I could start making juggernauts.  I used some new spells this game like Tidal Wave (so fun, but probably too powerful for so little mana!), Create Mountain, and Contagion.

Things I did to win

1.  Get an ally.  My ally was Resoln.

2.  Work the economy.  I played most of the game on Low so I could try to keep up in research and production with the AI.  I made money by selling stuff and rushing pioneers (is SD going to plug that exploit or is it a feature?).

3.  Choke points.  I used Raise Land and Create Mountain a lot so that I could control where the AI attacks would come from.  If the AI learned how to do those things themselves or learn how to undo them, it could be devastating to the player.

4.  Used an escaped juggernaut to chase me around the map destroying ally outposts so I could put down my own outposts instead.  Cheese, but it worked!

5.  Combinations of Tremor, Freeze, Wither, and Tidal Wave spells.  I noticed Wither and Freeze have a cool-down now though.

6.  I found it very difficult to play Yithril without any range troops so I stole the spirit of an Air I champion so I could haste my juggernauts.

Things the AI could improve on

1.  I'm sure this will be revisited in Beta 4, but I would like to see more specialization in AI cities.  Do they ever pick Training Yard for their army production cities?

2.  Use of strategic spells like Lower Land, Raise Land, Create Mountain, Tidal Wave and the use of direct damage overkill spells like Fireball and Blizzard.  On second thought, maybe the AI shouldn't do any of those things... it might be our only shot at winning on the higher levels. 

3.  You'll notice I made replica of Resoln using purple colors instead.  The blues of Pariden and Resoln are too similar so please change one of them.