Custom alien retaliation mission (with big angry MIB drop) spawns on big score or long time MiB HQ detected. When MiB HQ destroyed - base is safe and can't be retaliated with this way (only normal ufo method).
Instant karma on retaliation on failed HQ assault mission
Custom alien retaliation mission (with big angry MIB drop) spawns on big score or long time MiB HQ detected. When MiB HQ destroyed - base is safe and can't be retaliated with this way (only normal ufo method). Instant karma on retaliation on failed HQ assault mission