Black Pearl Cookie.

Formerly known as White Pearl Cookie, Black Pearl Cookie is the vicious sovereign of the Duskgloom Sea, impartially dragging countless vessels down into the abyss for her own amusement. She sits atop a foul throne of sunken wreckage and silently seethes over both the destructive nature of Land Cookies towards the sea and the long-ago betrayal of a Cookie once dear to her.

Black Pearl Cookie is the youngest sister of the Gem Mermaids: Crimson Coral Cookie, Aquamarine Cookie, Gold Citrine Cookie, and Mystic Opal Cookie. She was once attended to by Frilled Jellyfish Cookie before becoming her current self.

In her standard Cookie size, Black Pearl Cookie is an average-height and thin-yet-curvy mer-Cookie, though she scales up to be multiple stories tall in her true form. The mermaid has sickly light grey-blue dough and inky, full eyelashes with matching reflective eyeshadow. Her pupils are menacing black slits and her eye color is a powder blue. She wears a sadistic white smile and is usually seen coyly placing her hand near her mouth. As a sea-dweller, she has ear-like slate blue fins on either side of her head, webbed with three points each. Black Pearl Cookie's hair is a pearly white and takes a curly style that resembles sea foam. She has middle-parted bangs which curl upwards and reveal the caliginous pearl on her forehead. Instead of legs, she has a glittering fish tail in an onyx and stone blue gradient.

The Duskgloom Sovereign's torso is adorned with an obsidian, skin-tight bustier featuring a large, white scallop shell at her chest. Her arms are covered in black opera gloves with bat wing embellishments, and a tulle pannier skirt, shimmering in the light and resembling the bell of a jellyfish, sits around her hips. As ruler of her domain, she wears a black, webbed crown atop her head, adorned with five sharp spikes.

Black Pearl Cookie's main weapon is a vicious Aegean-blue trident. One of its prongs extends and curves upwards like a fish hook, and it is adorned with gleaming obsidian insets on its face and the end of its shaft.

Before she became the monster she is now, Black Pearl Cookie was once a kind Gem Mermaid under the name of White Pearl Cookie who harbored insecurities over her lack of special powers compared to her sisters. Still, it didn't stop her from doing the right thing; she saved the life of Lord Oyster, the young heir of House Oyster, and entrusted him with her pearl to protect him.

When she saw how the Land Cookies attacked her home, how Lord Oyster sold her pearl after she had entrusted it to him for safekeeping (despite his efforts to retrieve it), and the apparent death of her closest friend and servant, Frilled Jellyfish Cookie, at the hands of the Gem Mermaids, she was devastated and hurt to the point of transforming into something monstrous. She vowed to obliterate anyone or anything that would prevent her from achieving her desire for solitude in a sea where she could hear nothing but the currents, undisturbed by any ship. What was once her kindness and innocence was twisted into wrath and hatred for all the Cookies who dwelt on land.