The pact of Caim

Your patron is a vampire, a creature of the shadows, who didn't take all of your blood before put his own, making you a ghoulish creature. The motivations of these creatures are highly selfish, from wanting a companion to destroying a religious cult of light or obtaining a magical artifact. Some famous vampire examples are strahd von zarovich, The Dracula or even the prince Lestat.

Everything crucial about this subclass starts at level 1, so it will kinda overflow beginners at start and can look hard, but since you understands the basics the rest is pretty simple.

Expanded Spell List

Your undead nature 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.

Vampire Expanded Spells

SPELL LEVEL	SPELLS
1st	Fog Cloud, command
2nd	levitate, enhance ability
3rd	animate dead, cloudkill
4th	death ward, polymorph
5th	animate objects, telekinesis

Gothic resistance

Starting at 1st level, the blood that course in your veins transforms you in an undead. You are now:

- Resistant to necrotic damage;

- You can heal yourself from exhaustion and sickness by drinking fresh humanoid blood;

- You can see a total of 36 meters in darkness, if your race already let's you see this far in dark you gain an addtional of 9 meters.

-You no longer needs to breath

Unlive weaknesses

Besides the new night hunter abilities you now unlock you began to lose your humanity and start to feel weak with common day things. You're not alive and feels the vampiric curse corrupt your body, now you:

- Are vunerable to radiant damage;

- Are sensible to daylight: While you or a target are under solar light, you have disadvantage on attack rolls and perception checks related to vision;

- MUST sleep 8 hours per long rest ignoring any race trait that says the opposite (for example elf who needs to rest for just 4 hours);

- Need to carry a coffin to sleep your long rest. A coffin is a metal or wooden box in the size of your character ( small for a halfling, medium for a humam, etc...) and you need to attune to it to set a new one, your first coffin already is attuned to you. Without your coffin you can't sleep the long rest. While you're sleeping you're clearly a corpse, pale and not breathing.

-Running water and piercing damage of wood(like spears, swords and arrows) reduce  your moviment speed down to 0.

Tricks of night hunter

Starting at 6th level, you can use your vampiric nature to use the curse at your favor becoming even more monstrous. If you are not holding anything you can transform your hand in a claw to attack enemies. Your claw counts as a magic weapon for the purpose of overcoming the resistance and immunity of non-magical attacks and damage. To attack using your claw you add your proficience and your modifier of charisma, Strengh or Dexterity and they are Finesse and light weapons. It causes 1d6+Str/Dex/Cha.

Vampiric haze

Starting at 10th level, when you drop to 0 hit points, you can use your reaction to transform into a vampiric mist instead of dying. After doing this, you are stabilized and instantly teleport into your coffin, unless it's farther than 36 meters away. When using this feature, you need to spend your next turn incapacitated while your metabolism regenerates. While inside your coffin you regain 1d8 + your proficiency in hit points. On your next turn, you don't have to leave your coffin, you can just stay inside as long you remain incapacitated(after the second turn on your coffin it'll no more regenerates your health).

After using this feature, you must take a short or long rest to get it back.

ultimatum of the living

Starting at 14th level, you discovers that you're no vampire at all and this discovery frees you, once you controlled your undead condiction you now control your unlive powers, overcoming the curse.

-Your long rest is now just 4 hours on your coffin and can't dream anymore since you're canalizing your corpse nature so you're immune to magics that makes you dream like dream. 

-Running water and piercing damage of wood(like spears, swords and arrows) don't reduce  your moviment speed down 0 anymore, instead it just cuts your movement speed to half of it.

Curse contraction

Starting at 14th level, you drink your patron's blood and gain the power to develop vampire characteristics that were previously stunted. Once per long rest you can choose one of these to have:

-Develop your vampire fangs, once you make a melee attack, you gain one more attack action with your fangs, they have the same characteristics as your claws, but cause only 1d4 + Char / Str / Dex;

--Develop your vampiric regeneration, using your bonus action, you can withdraw 1d8 from your maximum health and recover 3d6 from your current health. The hit points you have taken come back on a short rest and You can use this ability as many times as your charisma modifier.

-Develop your blood-absorbing magic, after making an attack you can use your bonus action to heal exactly for the damage points you caused. You can use this ability as many times as your charisma modifier.

By the way, you can change between these abilities if you make a long rest or drinking your patron blood.