A shadow forged in fear...

[Enkhidu]

From what I remember, Cloak had the ability to actually draw out the shadow-stuff in semi-tangible form (or was that Shroud... I can't remember), so it wouldn't be out of line to use the different fog spells with a twist.

And really, the "with a twist" thing is going to need to be addressed no matter what - as is, spell selection in 3E will not fit the PC very well as the known spell list increases (there are only so many fear and darkness spells, after all). Therefore, I'd talk with your DM and tweak the existing spell list to better fit the character. Solid Fog, for example, could be portrayed as a thick blackness that impedes movement and obscures vision (mechanically the same, but with different flavor text).

 

[WayneLigon]

I'd still look at ShadowDancer; that 'walk through shadows' ability is wonderful for a Cloak-analog. You'll probably have to cherry pick spells but with the limited sorcerer spell selection that should be too hard. Just get your DM to agree on some flavor and visual changes and you can make almost any spell into a 'fear and shadow' spell.

0: Flare (actually a clinging burst of darkness), Ray of Frost (dark/ice), Touch of Fatigue, Ghost Sounds.
1: Obscuring Mist, Sleep, Cause Fear, Chill Touch
2: Darkness, Hypnotic Pattern (who says it has to be pretty colors and light people are looking at? Maybe they are frozen in horror at the terrible images they can see moving just inside your cloak.), Scare, Ghoul Touch
3: Hold Person ( Frozen with fear, like the ice/fear effect people had when they came out of Cloak's dimension.), Deep Slumber, Vampiric Touch, Blink (phasing through shadows)
4: Black Tentacles, Solid Fog, Fear, Phantasmal Killer
5: Shadow Evocation, Waves of Fatigue, Symbol of Sleep, Cone of Cold (darkness)
6: Symbol of Fear, Eyebite, Shadow Walk, Planar Binding (surely there are some kinds of shadow creatures out there to force into service)
7: Teleport Greater, Ethereal Jaunt, Insanity, Mass Hold Person
8: Maze, Trap the Soul, Symbol of Insanity, Polar Ray
9: Energy Drain, Weird, Shades, Mass Hold Monster

 

[Kunimatyu]

You want a Warlock for this guy. You really do.

Darkness as a spell-like ability an unlimited # of times/day? Check.
Devil's Sight ability to see through magical and normal darkness? Check.
Flee the Scene ability to dissappear into shadows? Check.
Tendrils of chilling shadow to kill his enemies? Check.

Seriously, look at Warlock. You should be able to get a Warlock to do the things you want to do, and talk with your DM to create a few more powers for him if you need to.

Also, from a story perspective, Warlocks are considered to gain their power from evil entities, whether by blood relation, a dark pact, or some sort of possesion schtick.

EDIT: Checked the CA list of warlock powers, and there are a ton of other darkness/fear-related powers I didn't mention up there. Probably even too many for a 20th-level Warlock to grab without spending feats.

 

[Terraism]

One thing to consider - and it may well go against your vision, so it's obviously disregardable - but if he's all about manipulating darkness, that doesn't necessarily rule out all blasting and buff-spells. I want to say there's a "Spell Thematics" feat somewhere that adds a certain theme, but I can't recall where - and I've also found that many DMs are ok (within reasonable limits) of allowing you to choose what your spells look like even without.

That said, there are a lot of spells that probably can't be made to fit the shadow theme, regardless - but there are some buffs and the like that possibly could. Take, for example, Cat's Grace. Shadows and darkness are often described as being fluid, which is pretty much Dexterity. If you described the Cat's Grace spell as him drawing the quickness of darkness into himself - even physically drawing in darkness for a moment, and then suddenly bursting with extra speed, it could well fit. I suppose my point is that, as WayneLigon pointed out with his example spell list, re-evaluating the appearance of many spells might broaden your options a bit.

 

[Naathez]

I must sincerely confess I like where this is going....

those ideas on hold person and especially hypnotic pattern are GREAT.

I've considered a warlock.... but he seemed a little too much of a one trick pony for the idea I have in mind. I wanted this character to find SEVERAL ways to use darkness.

guys you're all great , and helping a LOT... keep it coming...

 

[Phaedrus]

Either the current or the previous issue of Dragon has some new fear spells in it... you might take a look at those.

 

[Voadam]

Have all the spells be thematically darkness whether they are described that way or not. Either take the option from Quintessential wizard and apply it to your background, or take the FRCS feat spell thematics.

 

[Tinner]

You know a Minor Devil Bloodline wouldn't be amiss here either IMO.
It explains the whole "growing darkness within" thing. Plus you'll get darkness as an ability later on too, A Cha boost, etc. Good stuff all around.

 

[blargney the second]

I was going to suggest the Warlock as well, but it looks like that doesn't interest you. For what it's worth, I second the idea - warlocks have LOTS of darkness and fear-related abilities, and get to pick quite a number of them over the course of their careers.

-blarg