Right now, it seems like all the love for new creatures in Star Wars: The Last Jedi is going towards the porgs, but they’re not the only new bit of fauna in the upcoming sequel. As we’ve seen in the trailers, there are some crystal foxes and EW has shed a little light on the sparkly creatures. A singular crystal fox is called a vulptex, and a pack of them are vulptices. They live on the mineral-rich world of Crait, which used to be a hideout for the Rebel Alliance during the events of the original trilogy.

The vulptices roam around the salt flats and burrow deep with the crevasses and abandoned structures of Crait. “The idea is that these wonderful sort of feral creatures had lived on this planet and had consumed the planet’s surface, and as such had become crystalline,” says Neal Scanlan, head of the Star Wars creature shop. The designers took inspiration from “crystal glass chandeliers and the sort of luminosity and elements of refraction” they create. Aaron McBride designed the creatures.

So how did they translate them to the big screen? With the help of a very good dog:

“We had a little dog come in and we built a little suit for it, and we covered that suit with clear drinking straws,” Scanlan said. “It was amazing to see him run around. It could run and jump, and it had this wonderful sort of movement to it. It had a great sound to it, as well, because all the little straws moved and flexed with the animal.”

The dog’s movement then showed how the crystals might move on an actual animal and then they could build animatronic puppets and digital models. However, they’ll do more than just look pretty:

“They live within the burrows and within the tunnels beneath the planet,” Scanlan says. “So there is a time where their ability to shine within the darkness, should provide a guiding light to our heroes.”

Star Wars: The Last Jedi opens December 15th.