Now I feel a little bad about sticking with my level 30 build. But it's been such a PITA to make, I'm not inclined to revise backwards now unless it's needed. Consider this Thorn at her prime, which is the most important time to consider anyway, since as far as I'm aware, these writeups won't be played but instead exist mostly to inform our future choices and growth.
I think this is basically done now. I can touch things up a bit more, but unless I'm missing something, this should be ready to play. Even if it won't actually be played.

Some item slots have more than one item in them. Generally she wears the more powerful of the two, unless a specific need for the alternate comes up...then she switches. A few items have names in quote marks. These are her 'signature' items as I see it, and are associated with her in tales of her exploits.
Many items are from the Adventurer's Vault. I can provide expanded descriptions of their effects if needed.
[sblock=Thorn, Rogue 30][
Name: Thorn
Class: Rogue 30
Alignment: Unaligned
Race: Doppelganger
Size: Medium
Gender: Female
Abilities
Str: 12 [+1], Dex: 25 [+7], Wis: 14 [+2]
Con: 16 [+3], Int: 25 [+7], Cha: 18 [+4]
Hit Points: 173
Bloodied: 86
Healing Surges: 9 out of 9/day
Healing Surge hp gained :43
HP per level: 5
Action Points: 1
Speed: 9 squares
Armour Class: 41 (10+15 levels + 9 armor + 7 dex)
Fortitude Defence: 39 (10 + 15 levels + 3 con + 6 enhancement + 3 item + 2 feat)
Reflex Defence: 42 (10 + 15 levels + 7 dex + 6 enhancement + 2 class + 2 armor )
Will Defence: 38 (10 + 15 levels + 4 cha + 6 enhancement + 2 feat + 1 race)
Initiative: +7
Skills:
Arcana +30
Stealth +33
Thievery +32 (+2 open lock/disarm trap)
Acrobatics +27
Athletics +27
Bluff +32
Perception +26
Insight (Untrained) +23
Languages: Common, Elven, Dwarven, Draconic
Feats:
1 Arcane Initiate (Gain training in Arcana, gain Wizard at-will attack as Encounter)
2 Ritual Caster (gain ability to cast rituals)
4 Novice Power (Swap encounter powers)
6 Linguist (gain 3 languages)
8 Acolyte Power (swap utlity powers)
10 Adept Power (swap daily powers)
11 Agile Athlete (reroll acrobatics and athletics checks)
12 Combat Anticipation (+1 defenses against ranged, bursts and blasts)
14 Evasion (no damage from area attack misses targeting reflexes)
16 Mettle (No damage from area attack misses targeting Will and Fort)
18 Secret Stride (Movement doesn't penalize Stealth checks)
20 Fleet Footed (+1 speed)
21 Arcane Mastery (regain daily spell w/action point)
22 Blind Fight (ignore concealment/invis for adjacent spaces)
24 Unfettered Stride (movement unaffected by difficult terrain)
26 Inescapable Force (Force powers do full damage plus 1d10 to insubstantial creatures)
28 Great Fortitude (+2 Fort)
30 Iron Will (+2 Will)
Race Traits:
+2 Intelligence, +2 Charisma
+2 Bluff, +2 Insight
Mental Defense: +1 Will
Change Shape (At-will, Minor action)
Class Abilities:
First Strike - Combat Advantage against anyone who hasn't yet acted
Artful Dodger - +3 to AC vs opportunity attacks
Weapon talent - Inc shuriken dmg die, +1 to hit w/dagger
Sneak Attack +5d6
Epic Destiny: Deadly Trickster
Sly Fortune's Favor: Reroll any d20 roll 3/day
Trickster's Control: Enc or Daily power unexpended on 18 or more
Trickster's Disposition: 1/day force a 1 on GM roll
At-Will
Sly Flourish- +32 vs AC, 2W+7+4+6
Magic Missile - +28 vs Ref, 4d4+7+6+3 force, 20 sq
Shadow Stride, Move, From hiding move full speed to another hiding place and make unpenalized Stealth check, if successful your movement is hidden
Change Shape, Minor action, alter physical form to take on the appearance of any medium Humanoid, including unique individuals
Encounter
Thunderwave +28 vs Fort, 2d6+7+6 thunder, blast 3
Tornado Strike +32 vs AC, 2W+7+6 (slide targets up to 5, move 3), 1 or 2 foes, melee or range
Hounding Strike +32 vs Will, 3W+7+6 (combat ad 1 turn, gain +4 defenses vs that target), melee or range
Steel Entrapment +30 vs Fort, 3W+7+4 (immobilized 1 turn), blast 5, ranged only
Spectral Ram +28 vs Fort, 2d10+7+6+3 force (push 3 sq and knock prone), 10 sq
Master of Deceit, reroll Bluff
Leaping Dodge, interrupt - Roll Athletics +5 to jump away before attack hits
Daily
Assassin's Point +32 vs AC, 7W+7+6 (1/2 on miss), double sneak attack/crit, melee or range
Feinting Flurry +32 vs Will, 5W+7+6 (target defenses -4 for 1 turn, sustain minor), melee or range
Wall of Fire 1d6+7+6 adj, 3d6+7+6 pass through, 1 turn (sustain minor), wall 8x4 10sq
Disintegrate +28 vs Ref, 5d10+7+6 (ongoing 10, save - Ongoing 5 save), 10 sq
Dispel Magic, +28 vs Will (of creator), Conjuration/zone destroyed on hit, 10 sq
Arcane Gate, 2 empty squares, range 20, minor action, 1 turn (sustain minor), pass between target squares
Hide from the Light, from hiding become invis for enc, moving more than 2/turn or using other than basic attack ends
Epic Trick, minor action, regain HP and surges, save against all effects, recover encounter or daily powers (not this one)
Rituals
Arcane Barrier, 3200
Arcane Lock, 150
Comprehend Language 50
Conceal Object, 2000
Detect Object 1000
Disenchant Magic Item 360
Enchant Magic item 175
Endure Elements 100
Eye of Warning 4200
Fastidiousness, 50
Forbiddance 25000
Hallucinatory Creature, 2600
Hallucinatory Item, 250
Knock, 175
Linked Portal, 680
Magic Circle, 250
Magic Mouth, 50
Make Whole, 50
Memory Seal, 25000
Passwall, 2600
Phantom Steed, 360
Preservation, 100
Secret Page, 50
Sending, 360
Signal of Pursuit, 680
Silence, 75
Tenser's Floating Disc, 50
View Location, 5200
Cash: 67,345
Weapons
"Last Laugh" - Lucklender Dagger +6 (gains 1 charge every natural 1 or enemy crit, can spend charges to boost attacks)
"Hive of Motes" - Wand of Swarming Force +6 (Bonus to hit/dmg w/implement spells, +3 damage w/force spells, has Cloud of Daggers as Encounter power)
Bracers of Infinite Blades, 45000 (create +4 shuriken at will)
Armor
Swordwing Sylvan Armor +6 (Bonus to AC, Stealth and Athletics)
Neck
"Wink" - Liar's Trinket +6 (Bonus to defenses, also to Bluff, DC38 check to detect magic, contests Bluff vs divinations)
Head
"Clarity" - Eye of Discernment, 225,000 (+4 insight/perception, immune to blinding)
Goggles of Night, 21,000 (gain darkvision)
Feet
Sandals of Avandra, 625,000 (+2 speed, shift 1/2 speed at will, immune to OA per encounter)
Hands
Hedge Wizard's Gloves, 840 (mage hand and prestidigitation at will)
Guildmaster's Gloves, 425,000 (+5 Thievery and reroll 1/day)
Ring
Ring of Retreat, 65,000 (+1 sq when teleporting, daily to teleport to predetermined location, and back if within 10 hours)
Ring of Fey Travel, 325,000 (+1 speed, daily minor to teleport speed, lasts 1 turn on milestone)
Magician's Ring, 21,000 (Ghost sound and prestidigitation at will)
Waist
Belt of Vitality, 425,000 (+3 fortitude, use healing surge when making death save 1/day)
Wondrous
Flying Carpet, 125,000 (fly 6, up to 10 high at will, -2 AC/Reflex while on carpet)
Exodus Knife, 13,000 (create extradimensional hiding place)
Foe Stone, 13,000 (determine enemy type/vulnerabilities at will)
Unfettered Thieves Tools, 9000 (+2 thievery to open locks/disarm traps, can be used 5 sq away)
Rital Candle, 9000 (+2 to ritual skill rolls)
Handy Haversack, 5000 (store 1000lbs, weighs 1lb)
Rope of Climbing, 5000 (100' long, can climb 10' per turn and secure self)
[/sblock]
[sblock=Thorn's Story]
Excerpt from 'Last Days - A History of Endings'
by the honorable scholar Lars Jemen.
The name Thorn means different things to different people. Those who labor long and hard to impose law on others curse and use it as an epithet. Those who have been oppressed by restrictive tyrants often regard her as a sort of folk hero. Many in power believe that 'Thorn' was actually a movement, an organization of anarchists. Others strike closer to the truth and speculate a single operator who changes names and faces with the ease others change their clothes.
Thorn was a
doppelganger; strange creatures that were never shaped by divine hands and lack souls to anchor them into one form. They can change themselves to exactly resemble other races...even other individuals. Sinister and sly, the race was all but wiped out in the great wars but sometimes lived openly in the ages before, when Thorn lived. Like all doppelgangers, Thorn was doomed to die a final death. With no soul to carry on, she had neither afterlife nor hope of resurrection to look forward to. She lived for the moment therefore and was a creature of whim. She was driven by only a few real ambitions that shaped her actions.
Her first drive was simply to satisfy her own desires. She gathered wealth by fair means and foul, from legitimate business enterprise and from theft, extortion and cunning confidence games. With these funds she created a sanctuary for herself which has to this day never been discovered.
Thorn's calling card was unpredictability. She seemed to take a perverse joy in varying her patterns, goading those who hunted her into thinking they understood her next move, and then changing the game. She almost certainly had sympathetic ears close by her foes, feeding her their plans at crucial moments. Making matters worse was the fact that Thorn had made an intensive study of magic, giving her the means to use potent mystic protections and giving her unusual resources to draw on in her exploits. With a formidable arsenal of tools at her disposal, both magic and mundane, Thorn proved impossible to catch, impossible to stop.
Informing all her actions was the only real pattern to her behavior ever found; her sympathy for underdogs. Her very name was taken from the expression 'thorn in the side,' specifically referring to how she needled those who abused authority and power...which eventually came to be anyone who HAD authority and power by all appearances. Though this often placed her in the role of 'hero,' she was anything but heroic in her methods. Through infiltration, deception and sometimes a skillfully placed assassination, Thorn brought more than one powerful lord to ruin and disgrace. Of course, the cumulative effect of her efforts was to create chaos that contributed towards the ultimate collapse. At one point she even had the audacity to confront the emperor himself, one can assume intending to kill him. This went badly for her, and in fact nearly led to her death. She vanished for long years after that, and was much changed when she returned.
Thorn's return coincided with the discovery of the Egg of Aeons, it's now understood. Unfortunately at the time most believed her to be dead...a fact that played into her hands. It is speculated that her near-death reminded her of the grim fact of her mortality, and of the oblivion that awaited her. There are fanciful tales that spoke of Thorn breaching the very veil between worlds and bracing the gods themselves in their durances, to demand souls for herself and her kind. Proof that in the absence of the real article, imaginations run wild. Even so, one thing became certain; Thorn desired the Egg not for itself, but for what she could use it as a bargaining chip to attain. She was beyond the need for anything mortal agency could provide...now she sought leverage that would gain the attention of gods, demons and angels. The Egg of Aeons.
By her twin crafts of magic and deception, Thorn infiltrated not only the guardians of the Egg, but those who hunted the Egg. In the end she betrayed them both, and as they fought one another she took the Egg and vanished...presumably to a safe location from which to make her demands. Unfortunately for her, no plan, however subtle and intricate, long survives contact with the enemy...and she had made powerful enemies indeed.
The final confrontation of the Egg remains one of mystery. The warring factions were united, temporarily, by the theft of the Egg, and they managed to divine Thorn's intentions and moved as one to recover it. Their fate, and Thorn's, are unknown. The Egg never resurfaced, and the favor of the gods was lost. Mortal empires crumbled and the great war that had been started for the Egg consumed all in an age of darkness.[/sblock]