The animals you summon are incredibly powerful beings, forces of nature in their own right.
Prerequisites: Spell Focus: Conjuration, Augment Summoning, Animal Affinity, ability to cast 5th-level spells
Benefit: Each animal you conjure with any summon spell may gain the benefits of an animal growth spell for as long as it remains conjured, even if the animal is an outsider.
A feat that lets your summoned animals become a LOT more powerful. You could always cast this spell yourself if you’re a Druid or Ranger, but that would require another standard action and a second spell slot. This spell is even more powerful if you’re an arcane caster, as you get to add both a template and a spell. This feat makes even low-level summon spells viable at high character levels. To balance the incredible power of this feat, you have to really focus your feat selection as well as take a lackluster feat on the way.