I haven't done the flavor text for these, but here are four new hexblade prestige classes. Instead of +1 spell casting/level some of them have +1 hexblade spell casting/level - the first would be too powerful when combined with a regular caster. All of them have the same class skills and skill points as a hexblade. I also haven't done the requirements yet, but all should be hexblade/bab +5, with Knight of Misfortune requiring Aura of Unluck as well. Hmm, ok so these are really a work in progress
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craftyrat
Dire Hexer
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Dire Hexer level stack with hexblade levels for gaining access to hexblade
curse (including greater and dire curses) and Aura of Unluck.
1: Enhanced Curse (additional -1 to all penalties)
3. +1/day curse
4. Area Curse (curse can affect either a single target or everyone in a 5'
radius, at hexblade's choice)
5. Powerful Curse (-2 to save vs the curse)
Dark Mage
HD: d8
BAB: Good
F/R/W: Poor/Poor/Good
Dark Mage levels stack with Hexblade levels for spellcasting and familiars.
1. Familiar equal to level (not level minus 3)
2. Metamagic (Empower Spell 1/day without raising spell level or increasing
casting time)
3. Enhanced Casting (+1 to the DC of all Hexblade spells)
4. Enhanced Casting (+1 spell known of any spell level currently available)
5. Enhanced Casting (+1 spell per day of any spell level currently available)
Knight of Misfortune
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Knight of Misfortune levels stack with Hexblade for gaining access to Aura
of Unluck and spellcasting.
1. Extended Aura (double normal duration)
3. +1/day Aura of Unluck
5. Allied Aura (affects all allies in a 20' radius)
Familiar Knight
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Familiar Knight levels stack with Hexblade for gaining access to
spellcasting and familiar abilities.
1. Bonus Feat (Improved Familiar); Familiar at current level (not level
minus 3)
2. Familiar gains +2 to all saves
3. Familiar gains +4 bonus to natural AC
4. Familiar gains +4 bonus to Str, Dex and Con
5. Familiar gains Slippery Mind ability

craftyrat
Dire Hexer
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Dire Hexer level stack with hexblade levels for gaining access to hexblade
curse (including greater and dire curses) and Aura of Unluck.
1: Enhanced Curse (additional -1 to all penalties)
3. +1/day curse
4. Area Curse (curse can affect either a single target or everyone in a 5'
radius, at hexblade's choice)
5. Powerful Curse (-2 to save vs the curse)
Dark Mage
HD: d8
BAB: Good
F/R/W: Poor/Poor/Good
Dark Mage levels stack with Hexblade levels for spellcasting and familiars.
1. Familiar equal to level (not level minus 3)
2. Metamagic (Empower Spell 1/day without raising spell level or increasing
casting time)
3. Enhanced Casting (+1 to the DC of all Hexblade spells)
4. Enhanced Casting (+1 spell known of any spell level currently available)
5. Enhanced Casting (+1 spell per day of any spell level currently available)
Knight of Misfortune
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Knight of Misfortune levels stack with Hexblade for gaining access to Aura
of Unluck and spellcasting.
1. Extended Aura (double normal duration)
3. +1/day Aura of Unluck
5. Allied Aura (affects all allies in a 20' radius)
Familiar Knight
HD: d10
BAB: Good
F/R/W: Poor/Poor/Good
Familiar Knight levels stack with Hexblade for gaining access to
spellcasting and familiar abilities.
1. Bonus Feat (Improved Familiar); Familiar at current level (not level
minus 3)
2. Familiar gains +2 to all saves
3. Familiar gains +4 bonus to natural AC
4. Familiar gains +4 bonus to Str, Dex and Con
5. Familiar gains Slippery Mind ability