When summoning more than one dragon to a single terrain,
make sure they are the same color. Dragons of the same
color will attack your opponents' armies together; dragons
of different colors, on the other hand, will fight each
other every round until one is killed, ignoring the armies
at that location until their own battle is settled.
Don't forget that you can significantly increase your
magical versatility by capturing a terrain with a "standing
stones" icon at the eighth face. This allows you to cast
magic of that terrain's color, regardless of what race your
troops may be.