You can change your appearance and your voice. You determine the specifics of the changes, including your coloration, hair length, and sex. You can also adjust your height and weight, but not so much that your size changes. You can make yourself appear as a member of another race, though none of your game statistics change. You can't duplicate the appearance of a creature you've never seen, and you must adopt a form that has the same basic arrangement of limbs that you have. Your clothing and equipment aren't changed by this trait.
You stay in the new form until you use an action to revert to your true form or until you die.
Starting at 1st level, you gain the ability to place a baleful curse on someone. As a bonus action, choose one creature you can see within 30 feet of you. The target is cursed for 1 minute. The curse ends early if the target dies, you die, or you are incapacitated. Until the curse ends, you gain the following benefits:
You gain a bonus to damage rolls against the cursed target. The bonus equals your proficiency bonus.
Any attack roll you make against the cursed target is a critical hit on a roll of 19 or 20 on the d20.
If the cursed target dies, you regain hit points equal to your warlock level + your Charisma modifier (minimum of 1 hit point).
You can't use this feature again until you finish a short or long rest.
If you fail a saving throw or miss with an attack roll, you can roll 2d4 and add it to the total, possibly changing the outcome. Once you use this feature, you can't use it again until you finish a short or long rest.