Aura of Despair:
1) The visual effect - Casting of the ability looks absolutely awesome
Though would it be possible, to perhaps add a notification for other PCs who enter the aura, to actually know they entered the aura? Something in a line of simple notification - "You feel a sudden surge of dread/despair."
2) The mechanical effect... -2 Saving Throws seems like a pretty weak effect for ability, that needs actual 20 lvls of the prestige class
Suggestion #1 - Similar effect to Terrifying Rage ->
* Debuff: -2AB (+ -2 AC?) and -2 Saves
* Debuff: +20% Automatic Spell Failure
* 1/2 round stun (This one would be hard, as it could likely be cheesed by running back and forth, for infinite stun duration)
therefore:
DC for 1/2 round stun = (BG levels + (Hard Charisma modifier) +5) --> Therefore 20 BG with 20 base Charisma would have 30 DC on stun
Fiend Summon:
There seems to be a problem with size of the Summon and NPC Dragons. As summon will not attack, because it is unable to reach the dragon - while dragon keeps damaging it.
Suggestions? - Really have no idea how to deal with this. Either make the summon slightly smaller or increase his reach?