Patron Death's Mistress

Death's Mistress was once a mortal sorceress, who swayed the lord of the underworld after her demise. She now watches over the mortal realm anticipating each creature’s death and ensuring that it meets its end at the proscribed time and place. As queen of the Shadowfell, she rules over a decayed, dark reflection of the world.

Expanded Spell List

Your patron 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	cause fear, false life
2nd	gentle repose, silence
3rd	animate dead, speak with dead
4th	death ward, shadow of moil
5th	danse macabre, enervation

Murder of Ravens

Starting when you devote yourself to this patron at 1st level, you learn to summon ravens from the Shadowfell to deliver the souls of the dead.
Whenever a humanoid within 30 feet of you is reduced to 0 hit points and dies, you can use your reaction to summon a raven spirit in the square the creature occupied prior to its death. The spirit assumes the form and game statistics of a raven, and it always obeys your commands, which you can give telepathically while it is within 100 feet of you. A raven vanishes when it dies, if you die, or if the two of you are separated by more than 5 miles.
If you have a raven spirit previously summoned, and you summon another, the ravens flock together, and attempt to occupy the same space at all times. If you have 5 or more ravens flocking together in this way, you may permanently band the flock together as a swarm. The flock of ravens assumes the form and game statistics of a a swarm of ravens. The maximum number of raven spirits you can maintain at once is equal to half your warlock level.
In combat, the ravens and swarms move and act as a group and take their turn immediately after your turn. You control how the group acts.
If a raven is slain by a creature, or a swarm is damaged by a creature you gain advantage on all attack rolls against the creature until the end of your next turn.
At the end of a short or long rest, you can call all the ravens back to you—no matter where they are—and they reappear within 5 feet of you. At the end of a long rest, you may spend one spell slot to summon a number of ravens up to half your warlock level, but not exceeding the maximum.

Unceasing Servitude

At 6th level, your patron eases your mortal affairs by taking your soul to the Shadowfell. You no longer need food or water. You also don’t require sleep and can rest while remaining alert and performing light tasks. You must spend 8 hours resting in this way to gain the benefits of a long rest. In addition, magic can't put you to sleep.

Shield of Shadowfell

At 10th level, the Mistress grants you a protective blessing. You gain advantage on death saving throws, immunity to the frightened condition, and resistance to necrotic damage.

Right Hand of Death

Starting at 14th level, your patron bestows upon you the ability to channel the Shadowfell’s power to slay your enemies and bind their spirits to you. You can cast finger of death. After you cast the spell with this feature, you can’t do so again until you finish a long rest.

DM's Guild: Mordenkainen's Codex of Allies