The Tourmaline Turtle is an ancient Vis'tani artifact/vessel which allows those skilled enough to use the Planeshift ritual to move a group of people from plane to plane. It is currently in the possession of Quen Sandstrider.
The Tourmaline Turtle has two stages: active, and passive. In its passive state, the Turtle appears as a crystalline gem that can hang from a necklace or a wristband. It is roughly in the shape of a turtle and has a green-and-pink watermelon aesthetic.
In active mode, it changes into something resembling a submarine or other sea vessel. Instead of glass windows, it emits a semi-permeable membrane which allows passengers to enter and exit without doors.
To use the turtle for Planeshift purposes, the travel must be water-to-water. The Turtle will not activate outside of a water source. It also takes great magical skill - and sometimes some luck - to precisely land the Turtle where the ritualist intended.
Quen first read about the Turtle in Indar's journal. Later, when the Sandstriders were investigating The Mixer's house after her death, they found a list of artifacts which included the Tourmaline Turtle. The list indicated it was in the possession of Eighth Son, a Vitaurum crime boss.
When the Sandstriders defeated Eighth Son and forced him to take them into the vault, Quen immediately found and took the Turtle. The party was then able to use it to travel to the Faewild, and then to the Astral Sea to take part in the Astral Civil War. It was used fairly frequently during the war, as the Sandstriders traveled to various planes for various missions.
At the end of the Astral Civil War, the Sandstriders found themselves near the Temple of the One. The Turtle seemed to react to the energies of the Temple. When Cyric, Jenova, and Laz Ursulus disappeared through a rift in spacetime, Quen realized that it was reacting to the rift.
The Turtle switched to active mode, but looked different that its normal submarine configuration, and floated above the floor. The Sandstriders used the turtle to travel through the six Rifts. However, it was effectively destroyed during the journey to the Chamber of the One.