Pirates of Dark Water

Ren recovers the Fourth Treasure from the ocean floor. As Tula senses the approach of Dark Water, a shadow passes over the Wraith, someone in a balloon attempting to capture some of the evil liquid.

Ren and Niddler work to save the pilot, an alchemist named Cray, who at first glance mistakes Ren for his father Primus. Bloth shows up, but Cray is able to help them evade him, using a potion to envelop the Maelstrom in a massive mist cloud.

Back at her citadel, Cray offers the crew her hospitality and reveals that Primus was her suitor before he met Ren's mother. It soon becomes clear that Cray is still not over her failed relationship with Primus:

That night she sneaks into Tula's room and puts her into a deep sleep, refusing to wake her until Ren brings her a sample of Dark Water.

They do so, only to have the Wraith swallowed up by the Maelstrom. Ren pours some of the Dark Water into the hold, forcing Bloth to open the hatch to get rid of it, providing an escape.

Cray uses a single drop of the Dark Water in one of her potions, drinks it, suddenly becomes young again, and tries to seduce Ren. When that doesn't work, she steals the Treasures and keeps the crew as prisoners.

Konk and Mantus show up looking for Ren, and Cray strikes a deal with Bloth: The Treasures in exchange for the captain performing a marriage.

At the ceremony, Cray's hair becomes streaked with black and soon her body starts to decay from the Dark Water in her potion. She attempts to make an antidote but Bloth wrecks her laboratory, demanding the Treasures. To save Ren, Cray uses her magic to destroy her citadel. Ren tries to get her out too, but it's too late. Cray gives him her wedding bouquet, containing the Treasures, before dissolving into a puddle of Dark Water.

The crew laments Cray's sad life, controlled by her disappointment over Primus, before moving on.