Poseidon's Trident

Poseidon's Trident is a magical weapon used by King Poseidon. It was eventually stolen by his daughter, Ursula, who used it to turn her mermaid tail into tentacles in order to be like the Sea Goddess Ursula.

Before the Curse
Following the death of her mother, Ursula is commanded by her father, King Poseidon, to use her singing voice to lure sailors to their doom. One day, Ursula nearly leads Captain Hook and the crew of the Jolly Roger to their demise, but stops before they hit a group of sharp rocks. Ursula later leaves the sea, not wishing to abide by her father's rules. She starts working at a tavern as a singer in hopes of earning enough money to travel to Glowerhaven, a place her mother always enjoyed singing. She runs into Hook, who realizes she's the mermaid who almost got him killed, but since she didn't, he feels the need to buy her a drink. Hook agrees to take Ursula to Glowerhaven for free, but when King Poseidon tries to buy him off with squid ink in exchange for detaining his daughter's singing voice in a shell, the pirate alerts Ursula, who agrees to steal the squid ink for him instead so they may both get what they want. Before the two are able to set sail, however, Poseidon arrives and uses magic to get rid of the squid ink as punishment. Angered that his only hope of revenge against Rumplestiltskin has been crushed, Hook traps Ursula's singing voice in the shell so the Sea King can never use his daughter to sink another ship again. Poseidon tries to make up with his daughter later on, however, but Ursula is unforgiving, and instead she steals her father's trident to transform her mermaid tail into tentacles and takes control over the sea, deeming herself to be feared.