[Bananadine]

Disintegrate can do that too. I think Gift of Health might be another thing that can allow a unit to survive that kind of attack, sometimes. Maybe Opposition and Disintegrate have the same effect--sometimes hitting for about 1000 damage, sometimes hitting only just hard enough to kill or nearly kill the unit. I hadn't known Opposition did this, but I just tested it, and yeah, of my first two kills with the spell, one caused about 981 damage, and one caused 26 damage (which was just enough to kill).

Maybe the strong hit comes when the spell happens to beat magic resistance extra-hard, while the weak hit comes when it only barely beats magic resistance. Or maybe, once it has passed magic resistance, there's a totally independent roll that determines whether it hits hard or less hard. Or maybe it's something else.