Base combo: Warlock, Long night strider (or any other slasher feature), staff of the traveller, Agile Form, planewalker boots, Eladrin ring of passage, Initiate of the old faith, quick wild shape = two free action teleports every round for damage.
That leaves us with a minor action free (obviously). Thoughts on getting a teleport/shift there are: Seeker hybrid? Bloodbond requires your hybrid feat, but might be worth it. Eldritch panopoly works, but only works after a milestone. Kobold's too cheesy for me.
Ok, what about white lotus evasion? Only works half the time (ish), but that's probably good enough, particularly since all our standard action at will attacks will be arcane.
Need an at will attack that shifts. winners: Luring strike (shift+shift on a hit), pressing strike (the same). Luring strike has the edge here because of arcane synergy and WLMR.
Hmm. If we want to not lose half our out of turn damage, we need to be a half-elf and get an at will Beast power -- Savage Rend, with Unstoppable Beast to make it yet another shifty attack. Is there a way to retain our "damned if you do" out of turn, though? Can't use WLMR as a beast, though WLR works fine. [could also switch to hybrid druid and multiclass warlock--but then we'd be maining hellish rebuke for beastform turns, which gets a double-attack but no teleport. Or eyebite, which makes the aegis attack more likely on beast turns, but again, no teleport off the eyebite]
So far, we're talking Warlock/Swordmage, with a Druid multiclass (and probably windrise ports for a religious multiclass), and Radiant One at epic.
Hybrid Swordmage: Aegis of Assault Hybrid (Fey Pact)
At will powers: Eldritch Strike (warlock), Luring Strike (swordmage) (if human, Eyebite
Bits to stealborrow from the Arcane Slasher:
White Lotus Riposte/Master Riposte (White lotus enervation as well if we can fit it in after other hitbonuses) White Lotus Master Evasion (not actually stolen from AS). WTF? This is huge for this build; slash(+1PS) whenever you hit with Eldritch Strike or Luring Strike -- 1.5 extra slashes -per turn-. Arcane Admixture (frost) [though with two at wills to keep up, whetstone may be better] Lasting Frost Mark of Finding (oh, look, complete shutdown of their ability to attack friends without taking stupid damage if we can keep combat advantage..and we can. Not lfr-legal, though) charging aegis (if we have the space; free action mark at -3, but frankly they're not going anywhere; our attempted escape damage is a lot higher than WLMR, probably even in beast form) Arcane Familiar (but probably just fast hands if we can get the skill support) Versatile Expertise (staff and dagger? or something)
Gear: Planestrider boots (paragon) -- of course Eladrin ring of passage (paragon) Ring of Free Time (epic) +x shadow warlock starleather armor (we always have combat advantage, unless we're stunned or otherwise can't move) Gloves of Ice (radiant or necrotic = better; not all our damage is ice) Iron Armbands of Power (epic) Symbol of Divine Light +4 Pelor's Sun Blessing (level 3) (+2-3 damage; our wis is low) Cloak of Translocation (+2 to ac/reflex more or less always)Might reconstitute this , but we're better as long as we're juggling with an epic deep pocket cloak. fast hands x 2 is better than fast hands x 1. We might stop juggling soon, though. Syberys Shard of Merciless Cold (epic) (again, are we better with a radiant shard?) Rod of Corruption +1 (not that great without fey pact. If only we could always/never be in beast form out of turn and not need both eldritch strike -and- an at will beast attack.) Rod of Starlight +5 (radiant vulnerabilty ftw) Incisive Dagger +2 (cheap +teleport; needs juggling, though)
Combat advantage (for radiant one):
Shadow Warlock Armor means we always have this on our cursed target unless we're dazed or stunned. And even if we're dazed, we can free-action wild shape, teleport at least 3 (splitting it and ending up near where we started, likely), and get our attack in with radiant damage on our standard.
Grant radiant vulnerability: Might need to rely on quickcurse rod + starlight here, as reagants don't work on at-wills.
Fire vulnerability: good question.
Grant frost vulnerability: lasting frost. Our main weapon attack -must- do frost damage (admixture).
[hmm. ok, disembodied hand is a free action, not a 1/round free. That means we don't need fast hands or the deep pocket cloak, yeah (but costs us a feat]. Sweet. Go, go juggling.
Shadowrift blade++: gives us -another- slash whenever we hit. Wow!
Twofold pact. gets us our pact boon, and eyebite, and a second pact we don't care one whit for.
Shadow Walk: our extra damage relies on shadow walk. I'm not sure from compendium whether hybrid warlocks get Shadow Walk -- if not, we need to use hybrid talent to get it.
More later; need to play with this.