Squid Ink

"It wasn't the quill itself, but the Ink, what captured the Dark One... Harvested from the rarest species of squid, from the bottom of the bottomless ocean. Imposible to find, unless you're a mermaid, or me."

- Mr. Gold to Henry Magical Ink has the power to paralize magical beeings.

Before the Curse
Rumplestiltskin makes a deal with Cinderella so that she can asist to Prince Thomas ' ball in exchange of her first born, but when the Dark One returns for the price, Cinderella needs to find a way to keep her unborn child. The Blue Fairy gives her a quill with Magical Ink that can get the Dark One's magic frozen if he signs a contract with it.

Cinderella is meeting Rumplestiltskin and tells him she wants to alter the bargain. He tells her that is not what he does, she lies and tells him she's having twins. He asks her if she wants to give up both. She tells him her husband is having problems – the lands are poor and they cannot feed their people. She tells him she can have more children but she cannot make her land fertile. She tells Rumplestiltskin that if he signs on the dotted line and makes their land fertile he can have both children.

Rumplestiltskin takes the quill with the Magical Ink and tells her the only way to stop him is with magic. He tells her remember all magic comes with a price. He tells her if she imprisons him she will be even more in dept to her. He takes the quill and signs the contract and he is frozen. He tells her no one breaks deals with him and assures her no matter where she goes he will have her baby one day. ("The Price of Gold")

After the Curse
As Emma, Mary Margaret, Auora and Mulan are looking for a way to steal the Compass from Cora, Mr. Gold tells Henry a story that can help them. He tells him to fall a sleep and tell Aurora that he have some of the remaining Ink that Prince Charming, Snow White and Cinderella used long ago to paralize his magic in his cell. ("Into the Deep")

Trivia

 * It first appeared in The Price of Gold, but it wasn't mentioned untill Into the Deep.
 * The only way to get this Ink is beeing a mermaid or beeing under the Dark One's Curse to be powerful enough.