(HQ choice in a Codex: Chaos Space Marines army; counts as a Tzeentch-marked Chaos Sorcerer for the purposes of Thousand Sons being taken as Troops)

Shamash of the Cyclopean Sons
190 points

WS5 BS4 S4 T4 W3 I4 A2 Ld10 Sv3+/4++

Independent Character
Champion of Chaos
Mark of Tzeentch (included in profile)
Aura of Dark Glory
Psyker (Mastery Level 3) (knows all 4 Tzeentch powers)
Purist
Warpfield Manipulation
Punish the Insolent
Veteran of the Long War

Power Armour
Warp Knife
Bolt Pistol
Krak Grenades
Frag Grenades
Inferno Bolts

Purist - May not target himself with Boon of Mutation (though has no qualms about 'gifting' other characters).

Warpfield Manipulation - During your shooting phase, may, instead of shooting, target a unit within 12"; if an enemy unit, it must reroll any Invulnerable save rolls of '6'; if a friendly unit, it may reroll any Invulnerable save rolls of '1'. Lasts until the start of your next turn. If Shamash is already locked in combat when using this ability, he has -1A this turn.

Warp Knife - Melee, S-1, AP2, Master-crafted, Force, Channel - After inflicting a wound with the Warp Knife, may expend a warp charge to, instead of activating the Force ability of the knife, channel a psychic power through the blade, using the effects of Doombolt (inflicting 1 hit), Breath of Chaos (inflicting d3 hits), or Tzeentch's Firestorm (inflicting d6 hits), on the wounded unit. Not usable in this manner during a challenge, nor usable to channel a power that was used in the shooting phase this turn, nor against a vehicle without WS. Deny The Witch may not be used against this effect.

Punish the Insolent - If an enemy attempts to Deny The Witch against one of Shamash's Psychic Powers during the Shooting Phase, and is unsuccessful, Shamash may expend a Warp Charge: if a Psyker is in the attempting-to-deny unit or using a Psychic Hood, he suffers a Perils of the Warp; otherwise, a random model in the unit suffers a Perils.