Sounds like a plan.
SR = HD + 5?
It is considered to have exceptional attribute statistics (S 18/00, D 18, C 17, I 17, W 15, Ch 17 (to undead only).
Wraith has +6 Dex, +4 Int, +4 Wis, +4 Cha.
Maybe +6 Str, +6 Dex, +6 Int, +6 Wis, +6 Cha?
A wraith-king can drain life levels by gaze alone at the rate of one level per round for any one victim within clear view in a 30' range (the victim must save vs. death ray each round to avoid this effect).
Energy drain gaze.
Retain Con draining touch of normal wraith?
Any victim completely drained of life levels becomes a full-strength wraith under the control of the wraith-king.
Create spawn.
A wraith-king can cast either a permanent illusion or programmed illusion once per round, without limit. It can also cast a mass charm spell once per day. All spells are cast at the 15th level of ability.
Spell-Like Abilities: At will--permanent image, programmed image; 1/day-mass charm. Caster level 15th.?
A wraith-king is so powerful that any individual of a level lower than the wraith-king must make a saving throw vs. spells or flee in panic from fear.
Use lich's fear aura again?
The following spells or attack forms have no effect on a wraith-king: charm, sleep, enfeeblement, polymorph, cold, electricity, insanity, and death magic.
Borrowing from the lich...
Immunities (Ex): Liches have immunity to cold, electricity, polymorph (though they can use polymorph effects on themselves), and mind-affecting attacks.
A wraith-king can be harmed only by magical weapons with at least a +2 bonus, and even these weapons do only half damage.
DR 15/magic? Maybe add a special material or good?
A wraith-king is even more powerful than a lich. A cleric of level 9-13 has a chance to turn a wraith-king on a roll of 19 or better. A cleric of level 14 + has a chance to turn a wraith-king on a roll of 16 or better.
Lich's have +4 turn resistance. +6 or even +8 for these guys?
Because a wraith-king's undead power comes directly from a god, a raise dead spell will not affect a wraith-king.
Can only be restored to life by a cleric of the wraith-king's god?