the Dead Mists

Otherworldly
Patron
The beings that serve as patrons for warlocks are mighty
inhabitants of other planes of existence—not gods, but
almost godlike in their power. Various patrons give their
warlocks access to different powers and invocations, and
expect significant favors in return. Some patrons collect
warlocks, doling out mystic knowledge relatively freely or
boasting of their ability to bind mortals to their will. Other
patrons bestow their power only grudgingly, and might
make a pact with only one warlock. Warlocks who serve
the same patron might view each other as allies, siblings, or
rivals.
The Dead Mists
The Dead Mists of R'lyeh have for eons been a deadly trap
for astral travelers. Foolhardy wizards and mystics would
push themselves further and further into the astral sea, and
would eventually find themselves wrapped in the eldritch
mists. Lost and without guide, they would inevitably
succumb to the mist's soul-draining effects and would
become little more than food for the astral beings who slept
in the mists.
But the Dead Mists sometimes have plans of their own.
Inscrutably, the Mists sometimes claim a mortal host,
inhabiting them, empowering them, and guiding them
safely home. The Mists’ motivation is inscrutable and its
methods strange, but those empowered by it are made one
with the Mists, able to command it, or at least coerce it,
through the power of their own soul.

Eldritch Investigation

Starting at 1st level, you learn to open your mind to the Dead Mists of R'lyeh, granting you eldritch insights and power. As a bonus action, you can deal yourself necrotic damage equal to 1d8 times the level of your Pact Magic slots. At the start of your next turn, you regain an expended Pact Magic slot. Damage from this ability ignores both damage resistance and damage immunity, and does not subtract from your temporary hit points, if you have any. If this ability reduces you to 0 hit points, you are knocked unconscious, even if you have temporary hit points. You must be able to perform the somatic components of a spell in order to use this ability

Mist-Fueled Recovery

 

Mist Form

At 10th level, you learn to fully immerse yourself in the Dead Mists, transforming you in to a hazy, misty reflection of your true self. As an action, you can cast the spell gaseous form on yourself without using a spell slot.

Master of the Mists

At 14th level, you learn to infuse the Mists of R'lyeh into your spells, leeching vitality from your foes. Once per turn, when you deal necrotic damage to a hostile creature with a warlock spell, you regain hit points equal to 1d8 + your Charisma modifier.