The most comfortable and uncomfortable opponents for the Stronghold.

But if the Orcs reach your troops (and you can’t take them all out with Fireballs), your mages are doomed. Their defense is minimal against high attack power. However, if you equip them with self-made artifacts that boost initiative and cast a mass haste spell... and also level up their leadership... then the enemy troops will move very rarely (it has happened before...). In general, everyone has something to counter the Orcs.