I recommend taking A look at this spell: MQ16DagonAreaAttack1 (upto 5).
This spell makes NPC's and other Havok stuff fly into the air and fall to the ground. Maybe you could use it for the siege weapon you have in mind?
I dont want to use NPCs cause that would create insane lag... What I want for the siege, you are shooting at targets on the ground anyway you can, bow, magic, ballista, catapult, whatever. Each time you hit a target, or multiple targets with an AoE spell, ballista bolt wich goes through multiple targets, rock or whatever from catapult, you knock down whatever you hit. At regular intervals, enemy NPCs climb the ladder onto the wall, or use a siege tower, and fight you. Everytime NPCs go onto the wall, however many NPCs there are on the wall, that many targets disapear. If you hit a target, then the NPC affiliated with that target will not climb the wall. I want to know
A) Is that possible?
B) If so, how can you do it?