Celestial

The animal companion gains spell resistance equal to its level +5. It also gains: 1 — 4 HD: resistance 5 to cold, electricity and acid. 5 — 10 HD: resistance 10 to cold, electricity and acid, DR 5/evil 11+ HD: resistance 15 to cold, electricity and acid, DR 10/evil Smite Evil (Su): Once per day, the celestial creature may smite an evil-aligned creature. As a swift action, the creature chooses one target within sight to smite. If this target is evil, the creature adds its Charisma bonus (if any) to attack rolls and gains a damage bonus equal to its HD against that foe. This effect persists until the target is dead or the creature rests.