The fact that it has a 30% freezing chance, and 70% of the time you have creatures out, it will normally always freeze at least one because RNG says no.
1 creature out -> 30% chance of at least one being frozen
2 creatures out -> 51% chance of at least one being frozen
3 creatures out -> 65.7% chance of at least one being frozen
4 creatures out -> 75.99% chance of at least one being frozen
5 creatures out -> 83.19% chance of at least one being frozen
Therefore, if you have at least 3 creatures out, the chance is relatively close to 70% of at least one being frozen.