Cray is an alchemist and the one of Primus' former lovers.
She was voiced by B.J. Ward.
Cray is an alchemist that Ren and his friends saved from Dark Water when trying to collect a sample, and they found out that she was once involved romantically with Primus, and was in fact the "favorite" of all the court's ladies ("We had so much in common--music, travel, sailing...you couldn't have found a more perfect match...I was sure he was learning to love me..."), but broke off relations when she found out that she had competition in winning his heart.
After Cray saw Primus and the other woman picnicking together, she threw herself at Primus in a rage and ran off, and the lady providing the competition eventually married the king and become Ren's mother.
Cray left Octopon completely and became a reclusive alchemist, obsessing over Primus (and his "treachery") tirelessly, and her goal was to obtain a sample of Dark Water, under the guise of trying to use it for good, but she actually wanted it to make a potion to regain her youth, and to relive her "glory days" from roughly twenty years ago without the heartbreak that originally ended them. After running into Ren and the others, learning Ren's identity, and offering them food and rest in return for saving her life, she blackmails Ren into obtaining a sample for her (she says, "Because your father owes me! And you're the one that's going to pay," to Ren when he asks her why she's doing this).
She then makes the potion, regains her youth, and keeps all of them as her prisoners, stealing the Treasures, and (since ship's captains were granted the right to marry others, a fact from our seafaring past that must still hold true there) asks Bloth to marry her to Ren, in order to "fulfill her destiny" and latch onto her second chance to marry the prince of Octopon. (Throughout the episode, she almost exclusively speaks to Ren, even addressing him when others say something, and she's extremely sweet and courteous to him, but when she speaks to the others her tone is a little more cool and reserved, and she's obviously jealous of Tula, alternating between being overly sweet to her (usually when talking about Ren) and snapping at her.)
However, in the end, the Dark Water starts eating at her from within and then killing her, and she realizes far too late to save herself how futile her actions were and that she just couldn't let go of her past, and dies by dissolving into a puddle of Dark Water, but not before returning the Treasures to Ren as a "remembrance."