Infernal Armor (Su)

As long as he wears Hellknight armor, a 9th-level Hellknight gains a +2 bonus on all Charisma-related checks made while interacting with lawful, nongood creatures. In addition, while wearing the armor, he gains the ability to see perfectly in darkness of any kind, resistance to fire 30, resistance to acid 10, and resistance to cold 10.