In my view dragons should be there on the map, too powerful to steamroll over even with an army, and one way to make use of them is to throw a very difficult and costly spell that tries to control or bind the dragon to your channeler and his cause. If you suceed the others have something to worry about and you will have a great gaming hour. If you fail there is the risk that the dragon realizes it was you and comes gliding through the air towards your tower in a screaming, flaming rage. Interesting gaming time however it turns out ...!
I totally agree. The high risk/high reward factor of getting a dragon is going to add so much variety and replay value to each game and I love it. I like the idea of a spell, but would also love to have different options. Variety is the spice of life. Like having to do a difficult or lengthy quest for the dragon to gain its allegiance, bribe the dragon, cast a spell on it, etc. but if you don't bribe enough money, or fail the quest, the dragon might turn on you. Or let you live and go on its merry way. I just hope that there isn't a cookie cutter mold such as giving a dragon 100,000 pieces of gold and its yours every game, the same way, the same amount. That would ruin it for me.
Another thing I hope for is for dragons NOT to be a playable race. They're supposed to be extremely powerful units and having a faction like that would diminish their importance.
Just my 2¢