I think it might be interesting to come up with non-ritual spells of level 45 or less that will comprehensively defeat or destroy an army of 10000 or so for all the forms.
I'll take the easy one to start - Auram
The Dolorous Cloud Pe(Re)Au 30
Range: sight, Target: individual, Duration: concentration
This spell completely destroys the capacity of one cloud in the sky of up to 10 times base size to support breathing life and brings it down to ground level where it moves according to the will of the caster at up to the speed of a running man. Any creatures within the cloud start to suffocate as per the deprivation rules (ArM5, p180) and are at -3 to all rolls involving physical exertion. In addition, for each round of exertion a character must make a simple stamina roll of 6+ or lose a fatigue level. This may cause panic. Visibility within the cloud is approximately 10 paces. As this is an ongoing perdo effect, any fresh air conjured within the cloud instantly goes stale too. When the spell ends the cloud will return to its natural height but it will remain deadly to birds until it dissipates.
Base 3, +1 intensity, +1 rego requisite, +3 sight range, +1 concentration duration, +1 size