The Mechalich

Warlock's who take him on as a patron gain the ability to preserve their life, and take control of others bodies.

Form of Dread

You manifest an aspect of your patron’s dreadful power. As a bonus action, you transform for 1 minute. You gain the following benefits while transformed:

• You gain temporary hit points equal to 1d10 + your warlock level.
• Once during each of your turns, when you hit a creature with an attack, you can force it to make a Wisdom saving throw, and if the saving throw fails, the target is frightened of you until the end of your next turn.
• You are immune to the frightened condition.

You can transform a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

The appearance of your Form of Dread reflects some aspect of your patron. For example, your form could be a shroud of shadows forming the crown and robes of your lich patron, or your face might transform into bat-like features due to your vampire patron.

Defy Death

If you cannot already cast spare the dying, then you gain the spell.

Starting at 6th level, you can give yourself vitality when you cheat death or when you help someone else cheat it. You can regain hit points equal to 1d8 + your Constitution modifier (minimum of 1 hit point) when you succeed on a death saving throw or when you stabilize a creature with spare the dying.

Once you use this feature, you can’t use it again until you finish a long rest.

Consciousness Transferrence

You unlock the knowledge of The Mechalich.

You have the ability to pass your consciousness into an object. Doing so gives you the ability of unlimited life. While your body dwindles, your existence does not. 

Choose an item to put your consciousness into. As long as that object endures, so does your existence. Sir Amik Vazeere gives you a shard of the Heart Stone that can be used to pass into other bodies for you to control. You no longer need to eat, sleep, or breathe, although you still require rest to reduce exhaustion and still benefit from finishing short and long rests.

Create Thrall

You gain the ability to infect a humanoid’s mind with the alien magic of your patron. You can use your action to touch an incapacitated humanoid. That creature is then effected as if it has had the spell Dominate Person by you until a remove curse spell is cast on it, the charmed condition is removed from it, or you use this feature again.