Overhaul Changes

• Add class spell book (Wisdom based, casts as a cleric but no spontaneous spells) remove all feat-spells. See below.
• Possibly re-add Aura of Despair (level 2 ability). It'd be a feat that adds a supernatural aura that just applies an AOE that lowers saves around them to enemies only.
• Review summons. Some quick notes:
  
  • Fiendish Servant currently summons a Succubus, Vrock or at an expense of a feat at epic levels, an Epic Vrock.
    • These are underwhelming and except the last one, static in level
  • The actual description of the power is more akin to a Familiar (although a fiendish one!) then a random summoned creature. They level as per the characters full HD (previous class levels + Blackguard levels) which makes them scale a lot better and adds a new dynamic to the class.
  • Proper book Fiendish Servants have built in extra bonuses (eg Improved evasion, share spells, share saving throws, Blood bond and Spell Resistance) plus bonus HD/armor/strength based on level
    
    • If we can restricted animal companions this might be more interesting:
      • Add Animal Companion summoning to the class and restrict it to some fiendish familiars at level up (yes of course you get a choice between it or the druid/ranger one if you also have their levels)
      • Make each familiar fulfill some purpose:
        • One being a fiendish nightmare horse so can like a mount would be fun (possibly teleport the familiar itself to limbo and disable its AI/stop it moving while in horse use mode), and nightmare horses are just general all rounders
        • One be more defensive with Dex/AC - a smaller animal (+AC) for instance like a fiendish cat, with minor sneak attack
        • One be more spellcasting or ability based such as a fiendish imp, with a bit of magical resistances to boot
        • One be more attack-like, like a fiendish dog, more strength, better creature weapons and so ends up with more attack/damage
    • If we cannot restrict familiars we can make it either a bonus feat choice, or have it choosable by NUI or similar, when summoned it just uses a blueprint (akin to a familiar) to spawn at the right level/stats, or we use LevelUpHenchman for them.
      • TBH doesn't need to be an animal companion but seeing the stats on level up is useful and easier to change at levelup.
      • It would overlap a druid or ranger though...!
    • If we retain the Epic Fiendish Servant feat:
      • This should boost the servant in combat a lot more (bonus feats, resistances, stats, spells, maybe bonus levels). The Epic Vrock is rubbish but making a levelled one good would be perhaps better.

Overhaul Spellbook

Wisdom based, Cleric-style spellbook, no spontaneous casting. Using for now the spell list from this mod. There are some additions there that seem powerful but Blackguards get them so late it's lessened. These at least match the 3.0E list mostly and cover a bit more usability.

1st: Protection from Alignment, Bane, Divine Favor, Doom, Magic Weapon, Cure Light Wounds, Inflict Light Wounds, Summon Monster I
2nd: Bull's Strength, Eagle's Splendor, Darkness, Ultravision, Cure Moderate Wounds, Inflict Moderate Wounds, Summon Monster II
3rd: Greater Magic Weapon, Contagion, Poison, Protection From Elements, Cure Serious Wounds, Inflict Serious Wounds, Summon Monster III
4th: Fear, Freedom of Movement, Cure Critical Wounds, Inflict Critical Wounds, Summon Monster IV

Have added progression past 10th level where they gradually get more spell slots (but only level 4 spell slots).

We should aim to add some specific spells that Blackguards can use and would be good at using and shore up this list perhaps to be closer to the original spells list. This would be the 3.0E based version:

3.0E info for reference:

Spells: Beginning at 1st level, a blackguard gains the ability to cast a small number of divine spells. To cast a spell, the blackguard must have a Wisdom score of at least 10 + the spell's level, so a blackguard with a Wisdom of 10 or lower cannot cast these spells. Blackguard bonus spells are based on Wisdom, and saving throws against these spells have a DC of 10 + spell level + the blackguard's Wisdom modifier. When the blackguard gets 0 spells of a given level, such as 0 1st-level spells at 1st level, he gets only bonus spells. (A blackguard without a bonus spell for that level cannot yet cast a spell of that level.) The blackguard's spell list appears below. A blackguard has access to any spell on the list and can freely choose which to prepare, just like a cleric. A blackguard prepares and casts spells just as a cleric does (though the blackguard cannot spontaneously cast cure or inflict spells). Blackguards choose their spells from the following list: 1st level—cause fear, cure light wounds, doom, inflict light wounds, magic weapon, summon monster I*. 2nd level—bull's strength, cure moderate wounds, darkness, deathknell, inflict moderate wounds, shatter, summon monster II*. 3rd level—contagion, cure serious wounds, deeper darkness, inflict serious wounds, protection from elements, summon monster III*. 4th level—cure critical wounds, freedom of movement, inflict critical wounds, poison, summon monster IV*. *Evil creatures only.

Overhaul Description

(PRESTIGE CLASS)
A Blackguard epitomizes evil. They are nothing short of a mortal fiend, a black knight with the foulest sort of reputation. Many refer to Blackguards as anti-paladins due to their completely evil nature. No one class makes the best Blackguard, all that is required is a willingness to serve the forces of darkness.
 
WARNING: To cast a spell, a blackguard must have a Wisdom score of 10 + the spell's level. For example, to cast a 2nd-level spell, a blackguard must have a Wisdom of 12.

- Hit Die: d10.
- Proficiencies: All simple and martial weapons, all types of armor, and shields.
- Skill Points: 2 + Int Modifier.
- Class Skills: Concentration, Craft Armor, Craft Trap, Craft Weapon, Discipline, Heal, Intimidate, Lore, Parry, Persuade, Ride, Taunt.
- Primary saving throw(s): Fortitude.
- Base attack bonus: High (+1 per level).
- Spellcasting: Blackguard Spells. Divine (Wisdom-based, all spells are known, spell slots must be filled with specific spells, spell failure from armor is ignored).

REQUIREMENTS:

Alignment: Any evil.
Base Attack Bonus: +6.
Skills: Hide 5 ranks.
Feats: Cleave.

ABILITIES:

Level
1: Use Poison - Automatic success when coating a weapon with poison.
2: Smite Good - Add Charisma modifier to attack roll.
  Dark Blessing - Add Charisma modifier to saving throws.
3: Turn Undead - Make undead flee.
4: Sneak Attack +1d6.
5: Summon Fiend - summons a fiendish ally. This will increase in power as your character level increases.
7: Sneak Attack +2d6.
10: Sneak Attack +3d6.

EPIC LEVELS:

You are a twisted reflection of the epic paladin, radiating evil power from every pore of your body.

Hit Die: d10.
Skill Points at Each Additional Level: 2 + Int Modifier
Bonus Feats: The epic blackguard gains a bonus feat every three levels.
Special:
 Sneak attack: increases by +1d6 every three levels after 10th.

Epic Blackguard Bonus Feats List:
Armor Skin, Devastating Critical, Epic Toughness, Epic Weapon Focus, Epic Reputation, Epic Fiendish Servant,  Epic Prowess, Great Smiting, Improved Combat Casting, Improved Sneak Attack, Overwhelming Critical, Perfect Health, Planar Turning.