Name: Shinigami, aka Shini

Abilities: Enhanced teleportation & super strength

Appearance: Purple skin, bright green eyes, wears a black & bright green suit of armour & a black cape

Info: When the dark green skull first appeared on the back of Pia's right hand caused by her anger, Shinigami slowly began to take over, later enhanced by the Hell Energy left from slaying demons at Doom Slayer's dimension. 

Once Sadi unleashed Dracula Soma within Soma, Shinigami took full control and went on a killing spree.
Eliminating anyone that stands in her way to get to Sadi.

Fortunately however, Soma was later brought back to the light once more and steps forth to oppose Shinigami.
Convincing her to engage him in mortal combat.

Soma would have the upper hand at first thanks to his stone grey sword dripping a grey heavy ooze, using the ooze and the sword to turn Shinigami to stone over time.
Untill Shinigami unleashed her most powerful move and teleport from both sides to strike him with Bloody Mary.

Suddenly, Jade calls out to Pia as it would allow the Guardian Angel to be freed from Shinigami’s control briefly.
Soma uses this to his advantage and creates a massive cloud of grey petrifying smoke to turn both Shinigami & Pia to stone as she would say her last words to Jade before petrifying.

With the combined effort of Bugs Bunny using his Cartoon Force/pencil to erase Shinigami and to redo Pia back to good & Soma using a potion to free her from her petrified state, the Guardian Angel was reunited with her family and Shinigami was gone. For a time.

After a few anger management lessons given to Pia by Rita & realising she'd have nothing going down the path of evil, Shinigami switched sides.
Forming a bond over time with Pia thanks to Rita’s lessons and Pia’s acceptance of Shinigami, despite her panicking at first.

But one day, during Notori's tour of the multiverse, Pia's powers went out of control on her first signs of pregnancy.
Cutting her connection to Shinigami's power completely and only allowing Pia to summon her out of the dark green skull on the back of her hand next to Tenshi's white angel halo.
Regardless of this, Shinigami would carry on as Pia's guide just like Tenshi until death do them part.