Your patron is Acererak, once a cambion lich who grasped at godlike power only to lose his grip on reality. Now a vestige of his former self, the only way for him to truly exist is by granting power to mortals fool enough to seek his name and carve his sign.
EXPANDED SPELL LIST
Spell Level Spells 1st Detect Evil and Good, Inflict Wounds 2nd Hold Person, Ray of Enfeeblement 3rd Fear, Speak with Dead 4th Blight, Dimension Door 5th Hold Monster, Unhallow*
*(The unhallow spell functions just like the hallow spell, only it cannot produce the Courage, Daylight, or Energy Protection effects and requires, instead of herbs, the blood and ashes of once-living creatures. The unhallow spell does not fail if the radius includes an area already under the effect of a hallow spell, in fact, casting the unhallow spell on such an area dispels the existing hallow spell effect.)
Lichloved
Starting at at 1st level you have advantage on all Deception, Persuasion, and Stealth checks you make against Undead, and have resistance to necrotic damage. As an action you may detect the number and presence of, and the direction to, all Undead creatures within 60ft of you. Undead with an Intelligence score of 3 or lower are not hostile toward you without being provoked (though this non-hostility does not generally extend to any of your allies).
Paralyzing Touch
At 6th level, you may make a melee spell attack as an action. If this attack hits it deals 3d6 cold damage and the target must succeed on a Constitution saving throw against your warlock spell save DC or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. After using this ability you cannot do so again until you complete a short or long rest.
Armored in Death
At 10th level, your flesh hardens around your bones, going pale in color and cold to the touch. You gain resistance to cold and poison damage and are immune to the poisoned condition. While you wear no armor your armor class equals 13 + your Dexterity modifier.
Soul-Devouring Power
You gain additional arcanums: disintegrate at 14th level, finger of death at 16th, dominate monster at 18th level, and power word kill at 20th. Your spellcasting ability for these arcanums is Intelligence.
Any time you cast one of these additional arcanums you risk madness, forcing yourself to make a DC 23 Charisma saving throw with disadvantage. If your save fails, you experience 1 indefinite madness, and if both of the rolled dice would have failed the save you also experience a long-term and short-term madness (DMG pgs 258-260).