[MENTION=6789613]MessiahMushroom[/MENTION] so, my group's ghul lord saw play this weekend. Though only first level, looks like it'll be fun. I did make a change to the Enigma of Death feature, mainly because I don't have any of the homebrew spells mentioned in the list. So I went back to an older version of the feature (and one I had seen done elsewhere in another homebrew version of the Ghul Lord), and just made all spells of the necromantic school part of the sorcerer spell list for the archetype.
Also, a suggestion on the level six ability, Haematurgy. The current wording of subtracting hit points doesn't seem to take into account the almost continual temporary hit points from the at-will
false life feature. Say I have 7 temporary hit points, spend two Hit Dice to get a like number of sorcery points back, roll 6, still have 1 temporary left, and can re-cast
false life to get back the temporary points I lost.
Net effect - I spent a hit die, and lost an action casting
false life, which can easily be done out of combat. So I can use the sorcery point recovery, one hit die at a time, alternating with freely cast
false life, so as not to risk my real hit points.
This is really close to a complete free recharge of sorcery points during a short rest. It's just managing Hit Die as a resource between long rests, using them for SP or HP recovery. That's pretty powerful.
I'd suggest changing the effect to be more in line with some undead creatures abilities which drain life. For instance, a vampires bite: "The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, [...]. The reduction lasts until the target finishes a long rest."
That way, temporary hit points only add to the newly lowered max hit points, creating a real cost to recovering SP. Reducing Max Hit Points also negates the need to add wording for "can't be healed by [magic, regeneration, etc.]"
Also another point: what if you're reduced to zero hit points using this feature, either your version or my suggestion? I got SP back but I drop to the ground in a heap without getting to use it? To let a sorcerer use his sorcery point(s) before going unconscious, I'd change Haematurgy to a bonus action, and have being reduced to zero only affect the character at the end of their turn.
So, my revised version of the ability:
Haematurgy
Starting at 6th level, you gain the ability to draw from your own life-force to magnify your spellcasting abilities. As a bonus action, you can expend one or more Hit Die from your pool to regain lost sorcery points. For each Hit Die expended in this way, roll the die. Your hit point maximum is reduced by an equal amount, and you regain 1 expended sorcery point. This reduction lasts until you finish a long rest. If this reduction would reduce you to a hit point maximum of 0, then at the end of your turn, you fall unconscious but are stable.