Name: Disintegrate
Circles: ? / Destruction
Description: Target unit with fort? save less than X is destroyed. (9 resist in MoM)

OK, so in MoM Disintegrate either worked 100% or you couldn't cast it. So 8 or less resist units died from this spell in MoM.

I don't know what number of fort save to put as the threshold in WoM, but I like the idea of the threshold save value.