Harper allows a pure Int build. getting Int to +Hit and +Damage, but it doesn't cover the Dex prerequisites for the 2WF chain of feats.
o
https://ddowiki.com/page/Feats#Two_W..._Passive_Feats*
And Insightful Reflexes is covered by that feat.
(* Spoiler - Dex requirements are 17. You didn't say if you had any Tomes. If no, you could grab a +2 Dex tome this life, and be set. Or, if it's going to be a Dex build, grab +2 Int now (for the Skill Points & Trapping), take +2 Dex later (for gravy), done.)
Melee first, and (just?) enough Wiz to get the shroud.* Should be doable - can't say how much synergy there is, but doable.
(* That's not sounding like the classic "Pale Master/Pale Trapper" Wiz 18/Rog 2 blastem build that is around, and that I referred to, so ignore that.)
Unbongwah, who replied above (and quoted below), is one of the recognized "build gurus" on these boards, especially with off-beat, unexpected, or "flavor" builds that are targeted for fun and variety, high in concept rather than coldly calculated to min/max. Take a look at his suggestions, you'll be starting off in the right direction.
So, let's look at this, piece by piece... and a LOT depends on how much you want to rely on magic, and how much on "melee" as your source of DPS and survivability (and there's room for both, natch)...
VKF:
You said you had all the enhancement trees, so this is the no-brainer. Done.
Pale Master/Vampire:
o
https://ddowiki.com/page/Pale_Master...Core_abilities
You only need Wiz 3 and 6 AP to get shroud. It also gets you a pet, the Skeletal Knight, which you can either use as a 1 AP non-combat lever puller, OR feed to become something more "real" (altho' chasing it very far is pro'ly off-target for this build).
Wizard 6 (and 11+ AP) gets you one of the listed "undead augmentations" - and those can range from a simple "more hitpoints" to "less vulnerable to Light" to "+2 Assassinate" and beyond* - so that's widely variable. . (Tier III is proly about as high as you want to go in PM enhancements, 11-1
(* You get "Ghost Touch" from the EK tree, Core 3.)
Meanwhile, once you're shrouded, you want negative (self-) healing. There are some small boosts (+2% critical) in the tiers, but mainly you just want Negative spell power and the spells themselves. Core buffs are included in this list. (You may also want some offensive spells, but only ones with "No Saving Throw", since your DC's will be tragically low.)
- Wiz 3: Lesser Death Aura
- Wiz 5: Displacement, Haste (& Bonus Feat)
- Wiz 7: Death Aura, Dimension Door
- Wiz 9: Teleport, Waves of Fatigue
- Wiz 11: Greater Heroism, Tenser's Transformation (& Bonus Feat)
- Wiz 13: Greater T-port, Waves of Exhaustion
At first glance I'm thinking Wiz 7 is about the target, but Wiz 11 has a lot to speak for it (and I'm not taking lower-level "spell slots" into consideration). It's going to be a balancing act. :/
Eldritch Knight/survivabilty:
o
https://ddowiki.com/page/Wizard_Eldr...Core_abilities
Pretty clear you want the Core 6 here, for "-15% Arcane Spell Failure", and the +10 Universal (negative) Power (and Quickdraw - meh).
Going on to Core 12 doesn't add a lot - more -ASF that a 2WF rogue won't need, 2% doublestrike - and altho' Deflect Arrows is eye-catching, you will get that with VKF!. You will proly spend a lot of AP here, but that isn't calling for Wiz 12.
What other classes?
I was thinking that Ranger 6 might be handy - provides most of the 2WF feats for free, and (by itself) earlier than usually grabbed - but when three-classed w/ Wizard and Rogue, that becomes a looong wait for core feats, spells and class abilities - and I'm betting he won't be particularly feat starved.
But if you grab Wiz 7, then that leaves just enough for Rogue 12 & 1 more level TBD if you want to go for Rog 12 core enhancements - but do you? Assassin core 12 is meh. So maybe, maybe not?...
But wait...
At this point we have to ask - is this an 18-level build, to get to 20 and TR asap, or a 20-Level build, to either do some low-Epic farming or go on to 30? Because if you're going to TR right away, you won't see those last levels, 19 & 20, except for an eyeblink. Something to consider... so, with that in mind...
...Going past 6 in Rogue gives something good about every other level (and that's besides the Sneak Attacks). 8 gives Improved Uncanny Dodge, 10 gives a Special ability, and Rogue 13 gives a 2nd Special Ability. But...
Rogue 12 + Fighter 1 gives one extra Feat; Rog 11 & Fighter 2 gives two extra (and at whatever level you need them!). Rogue 6 gives Assassin's trick (which is all you really want), and Ranger 6 would give 2 more great trees to pull from (Tempest 2WF plus DWS melee goodness), plus all the feats you could want, plus Ranger stuff (a couple spells, +4 vs. a couple Favored Enemies) - at the cost of a more back-loaded build that will be a bit tougher to level. But if you're going to 30, that may be an investment worth the early delay.
Alternately, there's also Rog 6 plus Fighter 6 - lots of goodness there, and the Fighter levels can be placed strategically to get key feats asap. Different feel, but still strong.
The answers to those questions are up to you, only you know your playstyle best. :/