The Phantom

You have had an encounter with an otherwordly spirit that
offers its assistance to you if you are able to complete its goal
that it wasn't able to complete in its mortal life. While a
phantom could be mistaken for either a guardian angel or an
evil demon its intentions can vary from good to evil like any
mortal being. Phantoms can be the soul of a great hero or
the corrupted spirit of an avatar.

Expanded Spell List

The Phantom lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Spell Level     Spells 

  1st                Dissonant Whispers, Feather Fall

  2nd               Pass without Trace, Phantasmal Force

  3rd                Animate Dead, Speak with Dead

  4th                Death Ward, Phantasmal Killer

  5th                Dominate Person, Raise Dead 

Dead Sense

At 1st level, your patron grants you the ability to be more
connected with spirits and the undead. You gain proficiency in
perception, you get Spare the Dying as a bonus cantrip, and
three times a day you can cast Detect Evil and Good.

Ethereal Body

At 6th level, you are able to momentarily enter the Ethereal
Plane. As an action, you can enter the Ethereal Plane as if
you were casting Etherealness on yourself, but it will only last
1 hour or until you dismiss the spell as a bonus action. Once
you use this feature, you can't use it again until you finish a
short or long rest.

Deaths' Possession

At 10th level, you can possess any creature with a weaker will
than you. Once per long rest you can target a creature that
you can see and attempt to possess it as an action, the
creature must make a Wisdom saving throw against your
spell save DC. On a failed save you possess the creature for
up to 8 hours and you can't travel farther than 1 mile from
your body, your body also then becomes incapacitated and is
immune from all damage except fire and radiant. After the
possession ends you gain 2 exhaustion points, however, if you
end the possession before the fourth hour then you only gain
1 exhaustion point. On a successful save the creature doesn't
know that you tried to possess it and is immune to
possessions for 1 week.

Reaper Death Seal

At 14th level, you have the ability to seal a creature's soul away in a purgatory-like plane. Once per long rest, you can target a creature that you can see and seal its soul away as an action. The creature must make a Charisma saving throw against your spell save DC or its soul becomes banished. On a failed save the creature's soul is sent to a purgatory plane and its body becomes incapacitated for 1 minute, you must also maintain concentration throughout this process. If you kill the creature's body while its soul is in the purgatory plane, you heal yourself half of the damage dealt to the target. If you use this ability on an undead, they have disadvantage on the save, and on a failed save the undead soul is permanently trapped in the purgatory plane.