Strategy vs (black) dragons?

[jigoku]

Find/recruit Black dragons Yourself This way You'll be starting fights.
Get knights to Your army (they have dragon slayer as their characteristic by default), add maybe giants, horsemen etc.
Now cast mass haste 'cause kinghts & giants are really slow. Use fire rain/cold snakes etc. to destroy other enemies.
Ancient vampires + sacrifice helps a lot btw (better combo than using resurrection)