Giant Vermin

The vermin you transform with this spell gain DR 5/magic and either the advanced creature template or the giant creature template.

Augmented (6th): If you expend two uses of mythic power, any vermin you transform also gains either the agile or savage mythic template while the spell lasts.

If you're at least 9th tier and expend three uses of mythic power, the duration changes to instantaneous, meaning the vermin retain their giant size. After a number of days equal to your tier, you lose control over the vermin unless you have some other way of controlling them, and they lose the agile or savage mythic template but retain the advanced or giant creature template.