The Ordo Arcanum trained Ophiel as an assassin and spy, and taught him to unlock the arcane power hidden within his blood. He serves them covertly, operating under the codename "Cherub", by infiltrating secure government centres, observing the actions and conversations of those within positions of power, and removing them, permanently, when necessary.
I chose to multiclass into a Warlock for two main reasons: first, to pick up Eyebite so he could render himself invisible to certain targets when appropriate (to get Combat Advantage in a fight, or simply to bypass a guard in a non-combat encounter); and to grab Walker in Gloom from the Complete Arcane so he could gain the Warlock's Shadow Walk class feature. The former can be picked up with a single feat, but the latter requires 4 feats and the loss of a Paragon Path (like Master Infiltrator). Which kinda sucks.
I don't really mind, though. A lot of the less optimal rogue abilities can be swapped out for warlock abilities with a lot more Ophiel-esque flavor; many of them allow him access to some great teleports, which I think is pretty good.
Is there any way I can improve this character, though? I know the story is still very basic, and it'll be improved a lot in the days to come. I suppose the main thing I worry about is that I have to Paragon Multiclass in order to pick up Walker in Gloom so I can get Shadow Walk (which I really, really want), but it seems to me that Paragon Multiclassing is otherwise extremely weak. Sure, I get Eyebite as an At-Will, but I'll have to trade one of my existing At-Wills for it (both basic attacks; one that targets AC and another that targets Reflex - but I'd hate to lose either of them), and that's really as far as I want to go with Paragon Multiclassing. I have no desire to pick up a 7th level warlock encounter power at level 11, or a 10th level warlock utility at 12. I could even stand for Eyebite to remain an encounter power, so I could keep my rogue's at-wills.
All I really want is that Walker in the Gloom for Shadow Walk, but I'd be giving up all of the Master Infiltrator Path Features like Infiltrator's Action, Skillful Infiltrator and Invisible Infiltrator. Is that the way it's intended to work? I mean I understand losing out on the Encounters, Dailies, and Utilities granted by your Paragon Path, but to lose out on the Action Point bonuses and everything else is just, well, really, really weak. There seems to be no equivalent in the Paragon Multiclassing option.
I'm sure I'll get along just fine, though. I really like the character concept. It's probably worth mentioning that Ophiel isn't a "practicing" warlock; he doesn't study demonic texts or pledge fealty to some ancient power of the Feywild. He gains warlock powers by unlocking the power in his tiefling blood. Or at least, that's what I'm saying.
At any rate, how can he be improved?