I have another case of a map creating issue, this time with the illusion-summons

The situation is this: AI stacks move to a location after the timer expires. It's normally working better than I expected (they attack weak stacks that meant to block their ways) but there is one problem: the Legions have a persistent and cheaper summon option for scouting. It's not a normal unit, it's immune to everything and disappears after being attacked.

However, the AI stacks refuse to attack them which gives the player opportunity to use them to block the stacks' way indefinitely. How could I deal with that? Unfortunately, there is no way to ban particular spells (not that I know of anyway), otherwise I'd get rid of the troublesome illusions.