I've always found it both strange and disappointing that Shadow Mages aren't able to effectively take advantage of their synergies with Shadowdancer. To tackle this, I propose making Shadow Mage into its own prestige class that closely mirrors Shadowdancer, but with more tangible synergies with their caster class. This is my mockup from my brainstorming session.
Requirements - 3 Levels of Wizard or Sorcerer
Alignment Restrictions: Non-good
Multiclass Restrictions: Cannot have any levels in Druid or be a Wild Mage
Hit Die: d6
Proficiencies: None
Skill Points: 6 + Int Modifier
Class Skills: Bluff, Climb, Concentration, Craft Mastery, Heal, Hide, Listen, Lore, Move Silently, Ride, Sail, Search, Sleight of Hand, Spellcraft, Spot, Tumble
Primary Saving Throw: Reflex
BAB: +1/2
This class has a total of 10 levels. I wanted the class to be accessible in degree by both Wizards and Sorcerers, and not giving it Epic levels seems the best way to do that.
-=Class Feats=-
-=1st=-
-One with Shadows-
Grants +1 Hide per level in Shadow Mage
You gain +1 Arcane Caster Level for each level in Shadow Mage
-Shadow Weave-
You draw power from the Shadow Weave to cast your spells making your Arcane spells stronger in certain areas, but weaker in others.
Evocation spells (except for Darkness spells) are cast at -6 Caster Level with a -6 DC.
Transmutation spells are cast with a -6 DC.
You cannot cast Arcane spells if your primary or secondary diety does not grant access to the Shadow Weave.
Your Enchantment, Illusion, and Necromancy spells are cast at +2 Caster Level and their DC is increased by +2.
You are unaffected by Faezress and other Wild Magic zones
-=2nd=-
-Darkvision-
-Evasion-
-Uncanny Dodge I-
-=3rd=-
-Shadow Daze-
Identical to Shadowdancer's ability of the same name, except its DC scales off the higher of your Intelligence or Charisma.
-Summon Shadow-
Identical to the Shadowdancer's ability, except the summoned Shadow does not grant Improved Sneak Attack to the summoner.
The level of the Shadow is equal to [5 + SM Level + 1/2 Wizard or Sorcerer Level]
-=4th=-
-Shadow Evade-
Identical to the Shadowdancer's ability except it also scales with 1/2 your Wizard or Sorcerer level.
-=5th=-
-Defensive Roll-
-=7th=-
-Greater Shadow Daze-
Identical to Shadow Daze, except it affects enemies in a Large AoE.
-=9th=-
-Slippery Mind-
-=10th=-
-Shadow Displacement-
Identical to the Shadowdancer's ability.
-Epic Shadowlord-
If you have a combined total of 21 levels in Shadow Mage and either Wizard or Sorcerer, you gain the Epic Shadowlord feat.
-=Conclusion=-
This is obviously my own opinions and is likely a very rough sketch of the concept; subject to refining by someone more intelligent.
Moreover, I'd like to see more prestige classes in similar veins to Palemaster and Dirgesinger that create more unique and diverse caster-focused builds.