As of late, I have been preoccupied with creating a new class built around knowledge and information, perhaps predominantly for combat purposes but also for out of combat.
Here is the 3.5 feat from Complete Champion that first made me want to build a class around knowledge skills.
"You can use your knowledge to exploit your foes’ weaknesses and overcome their strengths.
Prerequisite: Knowledge (any) 5 ranks.
Benefit: Upon selecting this feat, you immediately add one Knowledge skill of your choice to your list of class skills. Thereafter, you treat that skill as a class skill, regardless of which class you are advancing in. Whenever you fight a creature, you can make a Knowledge check based on its type, as described on page 78 of the Player’s Handbook, provided that you have at least one rank in the appropriate Knowledge skill.
You then receive an insight bonus on attack rolls and damage rolls against that creature type for the remainder of the combat. The amount of the bonus depends on your Knowledge check result, as given on the following table.
Check Bonus
15 or below +1
15-25 +2
26-30 +3
31-35 +4
36+ +5
You can make only one Knowledge check per creature type per combat. If you fight creatures of multiple types during the same combat, you can make one Knowledge check per type, thereby possibly gaining different bonuses against different opponents."
Now here in the Paragnostic Apostle I found some interesting abilities (although many may not apply) that have inspired another potential class feature for my knowledge-based class. (Also from Complete Champion) Perhaps a bonus to be gained every 3 levels or so that may also give combat tricks/bonuses.
Knowledge Is Power (Ex): At each level, you gain a spellcasting enhancement based on your Knowledge skills. Each time you gain this feature, choose one of the following abilities for which you meet the skill-based prerequisites. Although you can choose some of these abilities multiple times (as indicated in the descriptions), you may not select the same one twice in a row, and the minimum required skill rank increases by 2 for each subsequent selection of the same ability.
Accurate Retort: You gain a +1 circumstance bonus on your ranged attack roll with every ray spell that you aim at a creature with a natural armor bonus. (Knowledge [arcana] 8 ranks).
Backhanded Attack: If you successfully hit with an attack that deals hit point or ability score damage and requires a saving throw against an additional, nondamaging effect (Such as an orb of acid spell), add 1 to the DC of the saving throw. (Knowledge [arcana] 6 ranks).
Call of Worlds: Each creature you summon with a conjuration (summoning) spell gains the fast healing ability. The damage healed per round begins at 2 hit points and increases by 1 for every three caster levels (maximum +5 at 15th caster level). (Knowledge [the planes] 6 ranks).
Discern Weakness: Choose one creature type or subtype from the ranger's favored enemy list (PH 47). If you have 8 ranks in the appropriate Knowledge skill (such as Knowledge [arcana] for dragons, or Knowledge [nature] for humanoids), the save DC of every spell that you target on a creature of that type increases by 1. You can select this ability multiple times, choosing a different creature type each time.
Divine Understanding: Choose one clerical domain. For the purpose of this ability, you can choose any domain, whether or not your deity offers it. Your effective caster level increases by 1 when you cast spells that appear on that domain's spell list. You do not however gain the granted power of the domain you select. You can select this ability multiple times, choosing a different domain each time. (Knowledge [religion] 5 ranks).
Energy Supremacy: Choose an energy type from the following list: acid, cold, electricity, fire. Your effective caster level increases by 1 when you cast spells of that energy type. You can select this ability multiple times, choosing a different energy type each time. (Knowledge [the planes] 5 ranks).
Manifest Ethos: Choose one non-neutral aspect of your own alignment (chaos, evil, good, or law). When you cast an energy-based offensive spell against a creature with an opposing alignment component (chaos/law or good/evil), one-half the hit point damage dealt is pure divine power instead of its normal energy type, and thus not subject to reduction by energy resistance or immunity. You can select this ability multiple times, assuming that your alignment permits it, choosing a different aspect of your alignment each time. (Knowledge [religion] 8 ranks or [the planes] 10 ranks).
Mind over Body: Your effective caster level increases by 1 when you cast conjuration (healing) spells or transmutation spells that grant ability bonuses or penalties. (Knowledge [nature or religion] 7 ranks).
Mind over Matter: Whenever you cast a spell that creates a solid object, itshardness and hit points each increase by 2. When you cast a spell that provides an armor bonus, that bonus to AC also increases by 2. (Knowledge [architecture and engineering] 5 ranks).
Mortal Coil: Your effective caster level increases by 1 when you cast spells that physically change the subject's form (such as alter self, enlarge person, or baleful polymorph). (Knowledge [nature] 6 ranks).
Noble Presence: Whenever you cast a charm spell, or a compulsion that affects the subject's emotions but not specific
actions (such as good hope or rage, but not dominate person), the save DC increases by 1. (Knowledge [nobility and royalty] 5 ranks).
Penetrating Insight: You gain a +1 bonus on caster level checks made to overcome spell resistance, or to successfully
dispel another caster's spell. (Knowledge [arcana] 9 ranks).
See through the Veil: Whenever you cast a necromantic spell i that targets undead, the save DC increases by 1. In addition, your effective turning level increases by 2, if you possess the ability to turn or rebuke undead. (Knowledge [religion] 7 ranks).
Spatial Awareness: Your effective caster level increases by 1 when you cast conjuration (teleportation) spells. Furthermore, the subject of any spell that increases base movement rate or grants a new type of movement gains an additional 10 feet to the designated speed. (Knowledge [geography] 5 ranks)
I’m hoping to use some abilities already in existence as the building blocks for this class.
Bardic Knowledge (Ex): A bard adds half his class level (minimum 1) to all Knowledge skill checks and may make all Knowledge skill checks untrained
Lore Master (Ex): At 5th level, the bard becomes a master of lore and can take 10 on any Knowledge skill check that he has ranks in. A bard can choose not to take 10 and can instead roll normally. In addition, once per day, the bard can take 20 on any Knowledge skill check as a standard action. He can use this ability one additional time per day for every six levels he possesses beyond 5th, to a maximum of three times per day at 17th level.
Monster Lore (Ex): The inquisitor adds her Wisdom modifier on Knowledge skill checks in addition to her Intelligence modifier, when making skill checks to identify the abilities and weaknesses of creatures.
There’s also the Loremaster prestige class, which has the Lore ability and some good thematic abilities.
Also potentially of note is some Master Spy abilities. Although not a knowledge expert per say, it does make you an expert of acquiring knowledge under adverse conditions and makes it difficult for others to pry knowledge from you.
Focused Trance (Ex): You can enter a deep meditation, blocking out visual and auditory stimuli and allowing you to concentrate on a single problem, philosophical issue, or memory. This trance lasts 1d6 rounds, during which time you can only take move actions. During this period, you gain a bonus equal to your level on all saves against sonic effects and gaze attacks. When you come out of your trance, you may make a single Intelligence-based skill check with a +20 circumstance bonus. You may enter your focused trance a number of times per day equal to your Charisma modifier.
Lore Keeper (Ex): Instead of encyclopedic knowledge, you learn most of your information through tales, songs, and poems. You may use your Charisma modifier instead of your Intelligence modifier on all Knowledge checks.
Think On It (Ex): Once per day, the oracle of lore can re-attempt any previously failed Knowledge check. On this attempt, add a +10 competence bonus on the check.
Final Revelation: You gain the ability to take 20 on all Knowledge skill checks. Your understanding of the fundamental underpinnings of reality has also become so advanced that once per day, you can cast wish. This ability does not require a material component, but the wish cannot be used to grant ability score bonuses, nor can it be used to replicate spells with expensive material components.
Current thoughts for the class:
Hit Die: d8
Skill Points at Each Level: 6 + Int modifier.
BAB: Mid
Fort Save: Poor
Reflex Save: Poor
Will Save: Good
Other: It needs ways to make Int matter somehow. (4 or 6 levels of casting, perhaps being able to add Int to AC, as a Duelist or similar to how a Monk adds Wis) ...and it needs class abilities focused around knowledge skills.
I can see this being an archetype of a Bard or Inquistor but I think it might need more tweaking than that.
Particularly in the spirit of the Inquisitor, I'm thinking of going for something more similar to Judgment than Knowledge Devotion, going something like this:
As a swift action, you can use your understanding of the enemy and magical prowess to gain an advantage over your foes.
...and then proceed to give options and scaling abilities to overcome your opponents, made larger as your knowledge checks increase.
I suppose I should know better than to make a post before actually finishing the class. Well, here's a rough outline of it:
EDIT: Class Name: Combat Librarian
...kind of a goofy name, which I'll lovingly call it until I come up with something more suitable.
Hit Die: d8
Class Skills: Acrobatics, Appraise, Bluff, Climb, Craft, Disable Device, Disguise, Escape Artist, Knowledge (All), Linguistics, Perception, Profession, Sense Motive, Spellcraft, Stealth, Survival, Swim, and Use Magic Device
Skill Ranks per Level: 6 + Int modifier.
BAB: Mid
Fort Save: Poor
Reflex Save: Poor
Will Save: Good
Weapon Proficiencies: Simple and Martial
Armor Proficiencies: None
No armor proficiencies?! O_O Well, we'll see. I'm toying around with giving the class a similar ability to a Monk's AC, except with Int. If I drop this idea, expect to see this class with proficiencies. ;)
Casting capabilities of a Bard except likely out of a spellbook and not spontaneous? ...and the spell list will need some adjustment.
Level 1:
Combat Knowledge, Lore, Knowledge Is Power
Level 2:
Knowledge Is Power, Bonus Feat
Level 3:
Level 4:
Knowledge Is Power
Level 5:
Lore Master
Level 6:
Knowledge Is Power, Bonus Feat
Level 7:
Level 8:
Knowledge Is Power, Improved Combat Knowledge
Level 9:
Greater Lore
Level 10:
Knowledge Is Power, Bonus Feat
Level 11:
Greater Combat Knowledge
Level 12:
Knowledge Is Power
Level 13:
Level 14:
Knowledge Is Power, Bonus Feat
Level 15:
True Lore
Level 16:
Knowledge Is Power, Imbued Recollection
Level 17:
Level 18:
Knowledge Is Power, Bonus Feat
Level 19:
Level 20:
Knowledge Is Power
(I'll need an appropriate capstone. ...I'll get there. :B)
What do all of these abilities do?
...hard to say. xD
Combat knowledge will give you certain bonuses based upon knowledge checks. Whether it will be an almost direct import of Knowledge Devotion or a modified version of the Inquistor's Judgments is a bit up in the air. D:
Knowledge is Power is also up in the air; I may move it to once every 3rd level, depending on how powerful I make it. I may also take some inspiration from Skill Tricks from Complete Scoundrel. Anyway, the main idea is that it will offer a number of abilities with ranks in certain knowledge skills as a prerequisite
i.e. You can't take a skill that requires 12 ranks in Knowledge (Engineering) until you have that many ranks in it. (So level 12 at the earliest)
Lore, Greater Lore and True Lore are all from the Loremaster prestige class. I think I'll keep Lore for sure, the other 2... We'll see.
The rest of the abilities all hinge upon how I design combat knowledge... so yeah, we'll see about that.
Another thought I had for this class was to make it rather mobile, as in giving bonus movement speed, a way to move outside of the move action (swift/immediate actions, or movement as part of a full attack action), and perhaps some lesser version of a Skirmish ability. (Like the Scout from Complete Adventurer or the Pathfinder Rogue Archetype, Scout) I'll probably have to drop these thoughts for the sake of balance, or reserve it for an option through the Knowledge is Power abilities. *le sigh* Can't have it all, I guess.
Still hoping to hear some of your thoughts and get some advice.
Take a look at the Archivist from Heroes of Horror. The 'Dark Knowledge' ability may be just what you are looking for. You can also use it as an alternate build for the class. Most home-brewed classes don't take into effect the idea of archetypes and abilities aren't normally set up to be swapped. Giving your 'Librarian' a support build w/bard progression and attack roles might be just what you want.
Dungeonscape also has the Factotum, which is a hodge-podge of abilities but is one of the few Int based classes and good inspiration for powers.
Dotted to read up later.
Factotum Inspired:
Brains over Brawn (EX, 1st level): Due to the extensive research the Combat Librarian undertakes as a part of his day-to-day activities, he has the ability to apply his mental prowess to physical endeavors. Starting at first level and every (2 or 3 levels) after, the CL chooses one Str, Dex, or Con-based skill he has at least one rank in. He gains an insight bonus to that skill equal to his Int modifier.
Possibly add: The skill does not need to be from the CL skill list.
Archivist Inspired:
Combat Knowledge: One + Int times per day(minimum 1), a Combat Librarian can draw upon his knowledge to grant himself and his allies a tactical advantage in combat. Doing this counts as a swift action. A CL unlocks new abilities as his level increases and can also call upon his combat knowledge more often, gaining one additional daily use at level three and every odd level after that(4/day at 3rd level, 5/day at 5th level, and so forth).
Using combat knowledge requires a Knowledge check of a type appropriate to the creature faced. A Knowledge (arcana) check reveals secrets of magical beasts, Knowledge (dungeoneering) pertains to aberrations, Knowledge (religion) covers undead, etc. The DC of the check is 15.
Most of the CL knowledge abilities increase in effectiveness if he succeeds on his Knowledge check by 10 or more. Combat Knowledge enhancements can only be used once against any given creature, though you may affect a creature with multiple enhancements.
A target creature must be within 60 feet, and the CL must be aware of the creature’s presence, although he need not have a line of sight to it. The effects of dark knowledge last for 1 minute, unless stated otherwise.
Knowledge is Power: Starting at first level you gain two enhancements to use your Combat Knowledge. At each even level after 1st, you gain an additional enhancement. Each time you gain this feature, choose one of the following abilities for which you meet the prerequisites.
Add in the sort of buffs the Archivist can use folded into your existing Knowledge is Power list. As it stands, you cannot choose any ability until level 5 yet because of your minimum ranks required. Making the choices mostly purchasable once and only against a specific creature/group of creatures in an encounter balances it against the fact they are party buffs. Or just take away the party-buffing part and make the abilities only personal.
Lowering the rank prereks or changing it to level-based is necessary, making the list spellcasting-only as opposed to expanding it into the Archivist area (which is a lot like judgments) will also keep the class distinct. Generalizing the bonuses to schools or subschools instead of much more specific instances, such as Noble Presence and See through the Veil, balances it against the limited number per day.
Another source of ideas could be Smilodans Prodigy class. Find it here.