Shadowlord+Assassin - Dips?

[Shin]

Hey there.

For my non-optimized 3.5 group, I did chose to play a sneaky, shadowy character.

Rogue3/XX2/Avenger2/TFSL6/Avenger7.
I want to build a sneaky character which deals lots of damage (sneak attack).
In combat, he does turn the battlefield into a shadowy area (darkness).
In that area, he jumps around and stabs his enemies (dimension door, shadow jump, shadow pounce).
In this area, he's in his element, gaining advantage over the enemy (darkvision, concealment, blind-fight, shadow discorporation).

Our DM modified the character progession system so that we can have up to 10 bonus charlvl feats (1 new at each uneven numbered character lvl or later, if we use the points on these instead of on stats).

Now my question is:
What are the best options to dip into with the two missing lvls (4th, 5th)?
Swordsage and ToB are not allowed at all.
I thought about Rogue2/Swashbuckler3, which would give me INT on dmg and weapon finesse for free, >and< more sneak attack, but I'd lose penetrating strike and wouldn't be able to deal any dmg to sa/crit immune enemies.
Fighter doesn't give me enough, I guess.
Maybe Factotum? Would give INT to my shadow discorporation so that I don't ever fail surviving.

Another question: Does it make any sense to use unseen seer for that build, in one way or another? As far as I know, unseen seer is more caster than anything else and should better be used in a build with as high CL as possible. So should I ignore it?

[docnessuno]

You could stop your TFSL progression to 4 and add 4 swashbuckler levels, for 2d6 SA, +1/+2 BAB, free feat and int to damage.

[eggs]

I hear some dashing fellow just put up a handbook on this! (http://www.minmaxboards.com/index.php?topic=8273.0;msg=131151)[/shameless] :smalltongue:

I'd probably go Totemist 2 for Blink Shirt and/or Girallon Arms or Monk 2 for Invisible Fist, Flurry, Carmendine Monk and extra feats.

If forcing sneak attack against immune targets is a problem, a Wand Bracer with wands of Golemstrike+Gravestrike+Vinestrike only costs 2550 gp and will probably last a good portion of your career.

EDIT: On Unseen Seer on an Assassin, it's usually something you'd consider in place of the Assassin's last level or two for an extra d6 of sneak attack or the extra spell known (Hunter's Eye is the big one). Since you're leaving assassin at 9 levels long, and Shadowlord is pretty useful for all 6 levels, US probably isn't worth it in this case.

[Shin]

The thing I'd want to have is 8 levels of assassin - to get HiPS.
I could spare 2 levels of it instead of one, but I guess that a character focused on shadow jumping to sneak attack won't profit that much from caster oriented classes. What I'm basically looking for - with the 2 free level slots - are the best improvements for jumping+sneak attack, darkness and shadow discorporation. If 2 levels of unseen seer are a good option, I take my chances.

I'd only need lvl 3 of swashbuckler to gain that INT to dmg, so rogue3/swashbuckler3 would be an option before going into assassin and TFSL.

The assassin handbook was the trigger for my question. I got some new tips through it and am now indecisive. Fighter2 doesn't seem to be the best option any longer. I'll check on your other suggestions, thanks for that part.