Your beast shape has taken upon a celestial or fiendish template.
Prerequisites: Beast shape class feature, Knowledge (planes) 5 ranks.
When you use beast shape to take the form of an animal, you can add the celestial template or fiendish template to your animal form. (Good beastmasters must use the celestial template, while evil beastmasters must use the fiendish template, neutral beastmasters can choose either). If your form has the celestial template and you score a critical threat against an evil creature while using your form’s natural weapons, you gain a +2 bonus on the attack roll to confirm the critical hit. The same bonus applies if your form has the fiendish template and you score a critical threat against a good creature.