Wow, that was more work than I thought.
Just gonna use the exact same format as the first poster to keep things consistent for the readers. Using 16,16,12,11,11,8 point buy. This might not be everyone's ideal build, but I liked it. Oh, and I didn't really get all that intense on my item selection.
Also, recall that Cursed enemies suffer +3d6 damage, and since you can curse two per round as a minor action, they should mostly be cursed!
H. P. Lovecraft, Half-Elf Warlock (Doomsayer, Demigod) 30[/b]
"When the void stares back at me, I spit in its face."
Code:
STR 14 +2 HP 180 bloodied 90
CON 28 +9 surge 45 per day 15
DEX 10 +0 AC 45 Fort 41, Refl 35, Will 42
INT 13 +1
WIS 13 +1 Init +19 Move 6
CHA 28 +9
Skills: Arcana +21, Bluff +29, Intimidate +29, Streetwise +29
Feats: Imp. Fate of the Void (total +2 to any roll after cursed foe dies.)
Action Surge (+3 to action point rolls)
Improved Initiative (+4 initiative)
Human Perseverance (+1 saves)
Twofold Curse (Curse effects two nearest foes)
Armor Prof. Hide
Armor Prof. Chain
Armor Prof. Scale
Armor Specialization: Scale (+1 AC, remove move penalty)
Lasting Cold (Cold dmg gives "Cold Vuln:5" to foe)
Wintertouched (Combat advantage when using Cold vs Cold vuln foe)
Psychic Lock (-2 to foe attack roll after using Psy. dmg)
Burning Blizzard (+3 cold/acid dmg)
Ritual Casting
Great Fortitude (+2 fort)
Lightning Reflexes (+2 reflex)
Iron Will (+2 will)
Devastating Critical (+1d10 crit)
Race: You all know this stuff.
Class: Curse (Curses two nearest foes, +3d6 dmg/hit), Star Pact Boon(+2 to any roll for the next round per Cursed foe that dies, cumulative), Prime Shot (+1 hit if no one else closer than you), Shadow Walk (concealed if move 3 squares)
Paragon: doomsayer's action (all cursed foes take 3d6 when u spend an action point), doomsayer's proclamation (all foes must roll two saves and take worse roll vs your fear effects), doomsayer's oath (when bloodied, +2 to attack rolls with fear)
Destiny: divine recovery (gain 90 hp when brought to 0 hp 1st time each day), divine miracle (regain one encounter power after using last encounter power)
At-will Attacks: 
Eldritch Blast: +30vsRef, 2d10+21 dmg

Dire Radiance: +30vsFort, 2d6+15 radiant dmg deals damage again if opponent moves closer on his turn
Encounter Powers: 
Coldfire Vortex: +30vsFort, 2d10+18 cold dmg + secondary attack on all adjacent targets, 1d10+19 cold

Fates Entwined (paragon): +30vsWill, 2d8+15 psychic dmg, until end of next turn target takes half dmg of any you take.

Strands of Fate: +30vsRef, 1d8+15 dmg, gains Vuln 11 to all attacks until end of your next turn.

Dark Transport: +30vsWill, 4d10+15 dmg; swap places with target and teleport up to 4 squares.
Daily Powers: 
Tendrils of Thuban: Burst 1 +30vsFort, 4d10+18 cold dmg, immobilize (Save ends); Sustain Minor: attack all in area for 1d10+18 cold dmg, immobilize (Save ends)

Long Fall into Darkness (paragon): +30vsWill, 4d8+15 psychic damage, stunned and prone; miss: half damage and dazed.

Thirteen Baleful Stars: +30vsWill, 5d10+15 fire/psychic dmg and target is stunned; miss: half damage and dazed.

Doom of Delban: +30vsFort, 5d10+18 cold dmg; miss: half damage. Sustain STANDARD, make another attack with this spell, adding a d10 for every time it has hit. The caster takes 2d10 dmg each time they sustain this spell.
Utility Powers:
Dark One's Own Luck: reroll any roll you choose (daily, interrupt)
Shield of Shades: reduce damage of any 1 attack to 0 (daily, interrupt)
Entropic Ward: All foes must reroll hits on you for one turn, +1 to any of your rolls next turn for each reroll, cumulative (encounter, minor)
Infuriating Elusiveness: teleport 4 squares, invisible until end of next turn (encounter, move)
Accursed Shroud (paragon): Curses foe; the foe targeted by this Curse must reroll all successful attack rolls for the duration of the encounter. (Daily, Standard)
Divine Regeneration (destiny): gain regen 28 (daily, minor)
Equipment: rod of reaving +6 (+6d8 on crit, 6 auto damage to any foe you curse), barkskin elderscale armor +6, amulet of false life +6 (daily minor: when bloodied, gain 45 temp hp), Ioun Stone of Truesight(darkvision, +6 perception/insight; daily minor: see invis), bracers of perfect shot(+6 dmg on basic range attacks), shadowfell gloves (daily: +3d6 necrotic to any spell), belt of iron skin (daily minor: +15 resist all weapons), winged boots (daily move: fly speed=normal speed til end of turn), ring of protection (+1 saves, daily interrupt: +2 one defense; +milestone use), ring of regeneration (+3 healing surge value, daily minor: regain 1 surge; +milestone use)