Magic wins games.
And Marveni has some awesome mages.
You could cast Army of Gold/Lead, Will of fates, Weapons of Sharpness, Strengh of Giants, Mass protection on your own troops.
Cast Doom, Swarm, Charm, Rust Mist, Blade Wind (excellent against glamour), Gifts from Heaven on the Enemy.
Don't forget to use Communions with Communion master and slave to make extra ultra powerful mages on the Battlefield. Also your Druids can Teleport to a province to help with defense. One or more of them laden with gems, casting spells can be a nasty surprise to any enemy.
...and the Holy grail is of course to cast Master Enslave. Forge Crystal shields, Star shine skullcaps, Crystal coins and use communions to get a caster up to S8 and watch the opponent's army disintegrate
