Statutory notice: Crumble has an attack component and (naturally enough) always hurts the castle defenders. Leprosy will always hit the besieging army. Manifestation can hit any commander in the province.
If you're a third party, my best guess is that other attack spells could hit either army at random.
Crumble can actually do a significant amount of damage to a stack of research mages and defending chaff. It's an absolutely awesome spell when you're sieging a major fort or cap for those reason.
The Following User Says Thank You to Sombre For This Useful Post:
I've never tried it before, out of fear. Began to think about it when I though about teleporting to siege a castle while casting destructive ritual spells. I was unsure about the order of events, assumed they would be random.