The Shapechanger.

Your patron is a mighty shapechanger, whose commitment to a single form is often fleeting. Your meetings with your patron may occur even in plain sight, as those around you may fail to see your patron for who they truly are. Succubi, lycanthropes, vampires, and even ancient mimics may grant such power to you in exchange for your service, and can offer you an untold number of ways to circumvent or overcome the problems before you—all by simply changing the limitations of your normal form. By releasing your body from itself, you stand to achieve great things together.

Level 1 Features:

Shapechanger Magic.

When you learn a spell of the appropriate level using your pact magic feature, you also learn the spells on the Shapechanger Spells table. The spells count warlock spells for you, and do not count against your spells known.

Regenerator.

Starting at 1st level, you automatically regain a number of hit points equal to your warlock level whenever you finish a short rest, up to half your hit point maximum. In addition, you have advantage on saving throws against any effect that would alter your form against your will.

Shapechanger's Strike.

Also at 1st level, you learn to channel the magic of your patron as an action, causing your body to warp in some way as you deliver an attack. For instance, your teeth or fingernails can sharpen as you deliver a vicious attack, or if you have a tail, it can grow sharp spines as you swing it. Make a melee spell attack against a creature within 5 feet of you. On a hit, the target takes 1d12 acid damage. After you make the attack, your body returns to normal.
The number of attacks you make, as well as the reach of the attacks, increases when you reach certain levels in this class: two attacks with a reach of 10 feet (5th level), three attacks with a reach of 20 feet (11th level), and four attacks with a reach of 30 feet (17th level). You can attack the same target or different ones with each attack, making a separate attack roll for each one.
You can always use an action to make this attack, even if your body is transformed by a spell.
Beginning at 2nd level, any Eldritch Invocation you gain that affects the Eldritch Blast cantrip also affects the attacks from this feature (except for invocations that affect the spell's range). If you later gain the Pact of the Blade feature, your reach with your pact weapon increases to match the reach of your Shapechanger's Strike whenever you make an attack with it as part of the Attack action. Similarly, if you are attuned to a magic item that grants a bonus to the attack rolls of your warlock spells, that bonus also applies to your spell attack rolls with this attack.

Level 6 Feature:

Malleable Form.

Starting at 6th level, you can cast the alter self spell at will, without expending a spell slot.
When you reach 14th level in this class, you also gain the following option when casting the spell:
Aerial Adaptation. You adapt your body to grow a pair of wings. You choose the appearance of the wings. For the duration of the spell, you gain a flying speed equal to your walking speed.

Level 10 Feature:

Quicksilver Mind.

Beginning at 10th level, your patron's malleability helps you adapt without the normal strains of typical spellcasting. You can use this feature in one of the following ways:
-When you cast alter self or target only yourself with a spell from your expanded spell list, you can choose for the spell to not require concentration. When you do, you can still choose to end the spell early (no action required).
-You can cast a spell from your expanded spell list that you don't know, expending a spell slot as normal and using the required casting time.
Once you use this feature, you can't do so again until you finish a long rest.

Level 14 Feature:

Shapechanger's Curse.

Starting at 14th level, your patron can curse the forms of the creatures you strike. Once on each of your turns when you hit a target with your Shapechanger's Strike, you can choose to have the target also make a Constitution saving throw against your warlock spell save DC. On a failed save, the creature is cursed by your patron. A cursed creature has disadvantage on attack rolls it makes against you and on saving throws it makes against transmutation spells you cast. The curse remains for 1 minute. At the end of each of the creature's turns, it can make another Constitution saving throw. On a failed save, the creature takes 1d12 acid damage. After three successful saves, the curse ends.
You can use this feature a number of times equal to your Intelligence or Charisma modifier (minimum of once), and you regain all expended uses of it when you finish a long rest.