Try this:
Focused Specialist, Chains of Disbelief & Spontaneous Divination Alternate Class Features
Banned Schools: Evocation, Conjuration, and Enchantment or Necromancy (My vote is Enchantment)
LEVEL CLASS FEAT
LVL01 Gnome Illusionist 01 Spell Focus (Illusion), Scribe Scroll, Heighten Spell, Earth Sense
LVL02 Illusionist 02 -
LVL03 Illusionist 03 Earth Spell
LVL04 Illusionist 04 -
LVL05 Illusionist 05 -
LVL06 Master Specialist 01 Spell Mastery, Skill Focus (Spellcraft)
LVL07 Master Specialist 02 -
LVL08 Shadowcraft Mage 01 -
LVL09 Shadowcraft Mage 02 Signature Spell (Silent Image)
LVL10 Shadowcraft Mage 03 -
LVL11 Shadowcraft Mage 04 -
LVL12 Shadowcraft Mage 05 Shadow Weave Magic
LVL13 Master Specialist 03 Greater Spell Focus (Illusion)
LVL14 Master Specialist 04 -
LVL15 Shadow Adept 01 Pernicious Magic, Tenacious Magic, Residual Metamagic
Pros: All illusion spells are extended, silent and stilled for free. You dont have to prepare any silent images as you can cast them via signature spell, and apply metamagic to it spontaneously to scale it to your needs. You also dont have to prepare any divination spells as you can cast those spontaneously as well.
Essentially this means you can cast any Evocation, Conjuration and Divination spell you know spontaneously. Fill all your slots with utility spells.
Save DCs for you Illusion spells are 15+Level+Int, and you have a +4 to overcome SR for anything without the Shadow Weave Magic feat.
-edit-
You can also take the ACF for illusionists that looses the bonus spell slots for specialization and gives you spell mastery for all illusion spells. Then you would have to let Signature Spell work without spell mastery (since the ACF pretty much does this without the need of spell mastery). This saves a feat and a school of magic.
Some great ideas; however, a few concerns. You are lacking Arcane Disciple and thus Miracles which kinda sucks.
At Level 5, the Gnome Sub level gives you free extend that should stack with Shadowcraft Mage's class ability. Spells lasting 4x as long (8x with Metamagic Rod of Extend?
) seems more powerful than spontaneous divination. Although I can see some cases where spontaneous access to the whole damn school (well at least the scribed spells post-errata) would be worth giving up the extra duration.
I wonder how powerful spending 2 feats for Signature Spell is. If the character is a focused Illusionist, that's 3 slots per level that can ONLY be filled with Illusion Spells anyway. Becoming an uber-sorcerer is nice, but your build gives up Miracle for it. I wish there was a way to fit both in, but with so few slots for utility and so many Illusion-only slots, I have a feeling Miracle Access ultimately gives more flexibility.
The above one is good, how about this?
Using the racial adaptation for SCM: 5 Illusionist/5 Red Wizard/5 Shadowcraft Mage
1 - Tattoo Focus, Scribe Scroll, Heighten Spell, Earth Sense
2 -
3 - Craft Wonderous Item/Earth Spell (Psychic Reformation to Earth Spell after crafting a Boccob's Blessed Book on the cheap)
4 -
5 - Spontaneous Divination
6 - Spell Focus: Illusion
7 -
8 -
9 - Arcane Manipulation
10 -
11
12 - Spell Mastery: Silent Image
13
14
15 - Signature Spell: Silent Image
Ban Conjuration for Red Wizard after using all your wealth from 3-5 to scribe good conjurations (like teleports) into your spellbook by borrowing a spellbook. Use Circle Magic + Arcane Manipulation + Ring of Wizardry + Spell Engine trickery to obtain obscene amounts of spells/day of your highest spell level. Circle Magic some cantrips up to level 20 spells, Arcane Manipulation those spells to level 1's. Then Circle Magic them up again to level 20's, and Spell Engine to swap them out for higher level spells. That's (4 + 60)*2 = 128 9th level spells per day as level 21 spells for 3 cantrips.
Also missing miracles. Although the human feat slot can allow for that. This seems almost TO, but if the player works with me to explain where he's getting all the people to give him slots, this is a possibility. He seems more interested in the master specialist version though.
If your DM lets you get Bluff4 and Hide4 at L1, go Illusionist1/SCM5/Whatever. Focused Specialist may be worth it, but I normally prefer normal specialist.
a) I am the DM
b) What early entry tricks are you suggesting? There is that "at least 4th level" spell prereq. Even DMM clerics need to be level 3.
c) I am not letting the player blatantly disregard skill ranks rules.
Thank you all so far!
