Paladin

gets additional Smite Evil use at each 5th level
Aura of Courage's ability of paladin now grants +4 saves vs fear to nearby allies
A paladin that takes any blackguard levels becomes a fallen paladin. As such:
- can no longer level up as paladin
- loses access to the smite evil feat
- loses access to the paladin spellbook
Paladin and blackguard levels stack for the following:
- divine grace and dark blessing saves bonus
- lay on hands heal
- smite good uses
- fiendish servant level
- caster level of blackguard spells
- sneak attack damage
The saving throw bonus from divine grace is limited by paladin (and blackguard) class levels.