You know, this origin story sounds awful familiar...
Quote Originally Posted by Shane McLaughlan
Lawful Neutral Human
Spellthief 1/Duskblade 3/Spellthief +1/Unseen Seer 3/Corrupt Avenger 4/Mage of the Arcane Order 1/Corrupt Avenger +6/Unseen Seer +1

Stats:

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Str: 16
Con: 14
Dex: 12
Int: 14
Wis: 8
Cha: 14

Level bonuses: 4th(Str), 8th(Str), 12th(Con), 16th(Con), 20th(Wis)


Story:

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Shane McLaughlan grew up an orphan. After showing a bit of magical ability, he was taken into the Order of the Arcane to maintain the grounds. His first job proved his most influencial. He grew to love the magic that coursed through his body and sought to improve his abilities. He struggled to learn more than what his innate talents offered him, but he never stopped trying. And through it all, he lovingly tended to the Order's needs -- he cleaned, maintained, and managed the grounds and buildings, gaining in responsibility as he grew. Soon, he managed the artifacts of the Order, keeping tabs of the libraries and labs.
One day, the Guild of the StickyFingers raided the Order. Shane responded to the invasion and fought the thieves with verve. His efforts were not enough and the thieves made off with several items and artifacts important to the Order. During the raid, the StickyFingers opened several vaults meant to contain the worst evils of the world. The tainted power of that evil spilled out into the labs and Shane found himself changed, even as he worked hard to help contain that taint back into the vaults.
His dark vow to take revenge on the Guild of the StickyFingers still burns hot in his soul.



Build:
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Shane McLoughlan
{table=head]Level|Class|Base Attack Bonus|Fort Save|Ref Save|Will Save|Skills|Feats|Class Features

1st|Spellthief 1|
+0
|
+0
|
+0
|
+2
|Comcentration 4; Disable Device 4; Hide 4; K:Arcana 4; Open Lock 4; Search 4; Spellcraft 4; Spot 4; Use Magic Device 4|1st: Craven; H: Able Learner|Sneak Attack +1d6; Steal Spell; Trapfinding

2nd|Duskblade 1|
+1
|
+2
|
+0
|
+4
|Concentration 5; Disable Device 5; Hide 5; K:Arcana 4; Open Lock 4; Search 5; Spellcraft 4; Spot 5; Use Magic Device 4|--|Arcane Attunement; Armored Mage (light)

3rd|Duskblade 2|
+2
|
+3
|
+0
|
+5
|Comcentration 6; Disable Device 6; Hide 6; K:Arcana 4; Open Lock 4; Search 6; Spellcraft 4; Spot 6; Use Magic Device 4|3rd: Axiomatic Bloodline; B: Combat Casting|--

4th|Duskblade 3|
+3
|
+3
|
+1
|
+5
|Concentration 7; Disable Device 7; Hide 7; K:Arcana 4; Open Lock 4; Search 7; Spellcraft 4; Spot 7; Use Magic Device 4|--|Arcane Channeling

5th|Spellthief 2|
+4
|
+3
|
+1
|
+6
|Concentration 8; Disable Device 7; Hide 8; K:Arcana 4; Open Lock 5; Search 8; Sense Motive 4; Spellcraft 4; Spot 8; Use Magic Device 4|--|Detect Magic; Spellgrace +1; Steal Spell Effect
6th|Unseen Seer 1|
+4
|
+3
|
+1
|
+8
|Concentration 9; Disable Device 9; Hide 8; K:Arcana 4; Open Lock 9; Search 9; Sense Motive 4; Spellcraft 4; Spot 9; Use Magic Device 4|6th: Power Attack|Sneak Attack +2d6

7th|Unseen Seer 2|
+5
|
+3
|
+1
|
+9
|Concentration 10; Disable Device 10; Hide 8; K:Arcana 4; Open Lock 10; Search 10; Sense Motive 4; Spellcraft 4; Spot 10; Use Magic Device 8|B: Silent Spell|Advanced Learning (Hunter's Eye)

8th|Unseen Seer 3|
+6/1
|
+4
|
+2
|
+9
|Concentration 11; Disable Device 11; Hide 8; K:Arcana 4; K:thePlanes 1; Open Lock 11; Search 11; Sense Motive 4; Spellcraft 4; Spot 11; Use Magic Device 11|MC: Obtain Familiar|Divination Spell Power +1

9th|Corrupt Avenger 1|
+7/2
|
+6
|
+2
|
+9
|Disable Device 11; Hide 8; K:Arcana 4; K:thePlanes 5; Open Lock 11; Search 11; Sense Motive 4; Spellcraft 4; Spot 12; Use Magic Device 11|9th: Master Spellthief|Armored Casting; Detect Sworn Foe; Sworn Foe +2; Taint Suppression

10th|Corrupt Avenger 2|
+8/3
|
+7
|
+2
|
+9
|Disable Device 13; Hide 8; K:Arcana 4; K:thePlanes 5; Open Lock 11; Search 12; Sense Motive 4; Spellcraft 4; Spot 12; Use Magic Device 11; Skill Trick: See the Unseen|MT: Planar Familiar|Tainted Strike 1/day

11th|Corrupt Avenger 3|
+9/4
|
+7
|
+3
|
+10
|Disable Device 14; Hide 8; K:Arcana 4; K:thePlanes 5; Open Lock 13; Search 14; Sense Motive 4; Spellcraft 4; Spot 12; Use Magic Device 11; ST: StU|--|Grim Resolve

12th|Corrupt Avenger 4|
+10/5
|
+8
|
+3
|
+10
|Disable Device 14; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 13; Search 14; Sense Motive 4; Spellcraft 4; Spot 13; Use Magic Device 11; ST: StU|12th: Cooperative Spell|Sworn Foe +4

13th|Mage of the Arcane Order 1|
+10/5
|
+8
|
+3
|
+12
|Disable Device 14; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 14; Search 14; Sense Motive 4; Spellcraft 4; Spot 14; Use Magic Device 14; ST: StU|--|Guild Member; Spellpool 1

14th|Corrupt Avenger 5|
+11/6/1
|
+8
|
+3
|
+12
|Disable Device 16; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 14; Search 16; Sense Motive 4; Spellcraft 4; Spot 15; Use Magic Device 14; ST: StU|--|Frightful Fury

15th|Corrupt Avenger 6|
+12/7/2
|
+9
|
+4
|
+13
|Disable Device 17; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 14; Search 16; Sense Motive 4; Spellcraft 4; Spot 16; Use Magic Device 17; ST: StU|15th: Craft Wand|Tainted Strike 2/day

16th|Corrupt Avenger 7|
+13/8/3
|
+9
|
+4
|
+13
|Disable Device 18; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 14; Search 19; Sense Motive 4; Spellcraft 4; Spot 17; Use Magic Device 17; ST: StU|--|Sworn Foe +6

17th|Corrupt Avenger 8|
+14/9/4
|
+10
|
+4
|
+13
|Disable Device 20; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 15; Search 20; Sense Motive 4; Spellcraft 4; Spot 18; Use Magic Device 17; ST: StU|--|--

18th|Corrupt Avenger 9|
+15/10/5
|
+10
|
+5
|
+14
|Disable Device 21; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 17; Search 21; Sense Motive 4; Spellcraft 4; Spot 19; Use Magic Device 17; ST: StU|18th: Enspell Familiar|Unnerving Fury

19th|Corrupt Avenger 10|
+16/11/6/1
|
+11
|
+5
|
+14
|Disable Device 22; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 19; Search 22; Sense Motive 4; Spellcraft 4; Spot 20; Use Magic Device 17; ST: StU|--|Sworn Foe +8; Tainted Strike 3/day

20th|Unseen Seer 4|
+17/12/7/2
|
+11
|
+5
|
+15
|Disable Device 23; Hide 8; K:Arcana 8; K:thePlanes 5; Open Lock 23; Search 23; Sense Motive 4; Spellcraft 4; Spot 21; Use Magic Device 19; ST: StU|--|Sneak Attack +3d6[/table]


Spells:
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Spells per day/Spells Known
{table=head]Level|0lvl|1st|2nd|3rd|4th|5th|6th|7th|8th|9th

1st|-|-|-|-|-|-|-|-|-|-

2nd|3/4|3/2|-|-|-|-|-|-|-|-

3rd|4/4|4/3|-|-|-|-|-|-|-|-

4th|5/4|5/4|-|-|-|-|-|-|-|-

5th|5/4|5/4|-|-|-|-|-|-|-|-

6th|6/4|6/5|-|-|-|-|-|-|-|-

7th|6/4|6/5|3/1|-|-|-|-|-|-|-

8th|6/4|7/5|4/2|-|-|-|-|-|-|-

9th|6/4|7/5; 0|4/2|-|-|-|-|-|-|-

10th|6/4|7/5; 1|4/2|-|-|-|-|-|-|-

11th|6/4|7/5; 1|4/2; 0|-|-|-|-|-|-|-

12th|6/4|7/5; 1|4/2; 1|-|-|-|-|-|-|-

13th|6/4|7/5; 1|6/3; 1|-|-|-|-|-|-|-

14th|6/4|7/5; 1|6/3; 1|0|-|-|-|-|-|-

15th|6/4|7/5; 1|6/3; 1|1|-|-|-|-|-|-

16th|6/4|7/5; 2|6/3; 1|1|0|-|-|-|-|-

17th|6/4|7/5; 2|6/3; 1|1|1|-|-|-|-|-

18th|6/4|7/5; 2|6/3; 2|1|1|-|-|-|-|-

19th|6/4|7/5; 2|6/3; 2|2|1|-|-|-|-|-

20th|6/4|8/5; 2|7/4; 2|2|1|-|-|-|-|-[/table]

Duskblade Spells (including Int bonus)
Corrupt Avenger Spells (NOT including Corruption bonus)

Spells Known (cumulative):
1st: --
2nd: 0th: Acid Splash; Disrupt Undead; Ray of Frost; Touch of Fatigue 1st: Chill Touch; True Strike
3rd: 1st: Detect Chaos; Resist Energy
4th: 1st: Expedious Retreat, Swift
5th: 1st: Shocking Grasp
6th: 1st: Ray of Enfeeblement
7th: 2nd: Dimension Hop; Hunter's Eye; Locate Object
8th: 2nd: See Invisibility
9th: 1st: Endure Elements; Read Magic
10th: 1st: Detect Poison; Detect Undead
11th: 2nd: False Life; Vampiric Touch
12th: 2nd: Shatter; Summon Swarm
13th: 2nd: Spider Climb
14th: 3rd: Dispel Magic; Remove Curse
15th: 3rd: Haste; Speak With Dead
16th: 4th: Evard's Black Tentacles; Freedom of Movement
17th: 4th: Death Ward; Enervation
18th: 3rd: Protection from Energy 4th: Cloak of Hate
19th: 3rd: Discern Lies 4th: Phantasmal Killer
20th: 2nd: Melf's Acid Arrow


Level 5:
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Welcome to Spellthief 2/Duskblade 3.
This character is, essentially, a trapfinding scout. Good spot keeps him aware of the world around him. Good search and disable device with the trapfinding ability makes him able to find those pesky traps and take care of them. Hide is a good skill at this point, as long as he stays away from scent-sniffing dogs.
In combat, Sneak Attack couples with Craven and Steal Spell (and Steal Spell Effect). Stand back, fire shuriken or sling stones or such from concealment. Or step up with a sword and use Arcane Channeling with Chill Touch or Shocking Grasp.
Magically, there are options here. Detect Magic at will is nice. Resist Energy helps in combat or with some traps and is a useful utility for exploring into deserts, arctic regions, volcanoes....



Level 10:
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Unseen Seer 3 and into the SI!
Trapfinding continues to be the forte. Find 'em and take 'em apart! The spot skill keeps pace for scouting and the skill trick (see the unseen) is useful in many situations. An imp as a familiar adds a second pair of eyes (using its master's skill ranks) to scouting, using flight, invisibility, and darkvision. (Check with the DM to see if stealing a spell effect works on a SLA. If so, the imp goes invisible, his master steals the effect to become invisible himself, then the imp uses invisibility on himself again.)
In combat, Sneak Attack remains priority. The imp uses alternate form to become a boar and a flanker! With Master Spellthief and Divination Spell Power increasing caster level for Hunter's Eye, sneak attack gets wicked. (Check with the DM to see if the game allows the opportunity to use Steal Spell multiple times on one attack.) Add power attack to the craven damage and Tainted Strike when the situation allows and calls for it.
Detection is easy at this point. Detect: Magic, Poison, Undead, Chaos, Sworn Foe are all spells (or SLAs) in the arsenal. Add in spells See Invisiblity and Locate Object. The imp adds Detect Good and a Detect Magic of his own.



Level 15:
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More of the SI and one level of Mage of the Arcane Order.
Search and Spot continue along. Disable Device and Open Locks follow suit. All usable by the familiar, too. Scouting and trapfinding continue to be easy.
Combat hasn't changed much. It hasn't had to. Another Tainted Strike per day is nice. A third iterative attack per round is better. Haste and Vampric Touch help in melee. Summon Swarm annoys those enemy casters.
Magic abilities open up wide now. Remove Curse and Dispel Magic are nice for trapfinders to have in their back pockets. Spider Climb helps travel. But the biggie is access to the Spellpool. ANY 1st-3rd level wizard/sorcerer spell in the game. Also the Craft Wand feat. Combined, those grant amazing utility! And the imp can use his master's skill ranks (with his own Cha bonus) to auto-succeed UMD checks to activate those wands.



Level 20:
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Finish the SI and another level of Unseen Seer.
By the end, Disable Device, Open Lock, and Search all hit max ranks. Spot and UMD are not far behind. Devices and mechanics are your wheelhouse. Finding most anything is still easy with all the detect spells.
Combat continues to a fourth attack each round. Power Attack and Craven are deadly. The Enspell Familiar feat allows the imp to gain sneak attack through Hunter's Eye and still maintain a flanking postion. Evard's Black Tentacles + Freedom of Movement is always a fun combination.
Magcially, Death Ward and Protection From Energy add to survivability. Discern Lies and Speak with Dead open abilities to find more info.



Items:

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Ring of Wizardry (I or II or even both) (DMG)
Wands, wands, wands in wand chambers, in pockets, stuffed down socks, in the familiar's hands, hidden in unholy and unusual places. Oh, and did I mention, WANDS!


Resources:
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Classes/PRCs:
Spellthief -- Complete Adventurer
Duskblade -- Player's Handbook II
Unseen Seer -- Complete Mage
Corrupt Avenger -- Heroes of Horror
Mage of the Arcane Order -- Complete Arcane

Feats:
Craven -- Champions of Ruin
Able Learner -- Races of Destiny
Axiomatic Bloodline; Enspell Familiar -- Dragon Compendium
Power Attack; Silent Spell; Craft Wand -- PHB
Obtain Familiar; Cooperative Spell -- Complete Arcane
Master Spellthief -- Complete Scoundrel
Planar Familiar -- Planar Handbook