Crystal (Crystalia Amaquelin) is a fictional superhero appearing in American comic books published by Marvel Comics. Crystal first appeared in Fantastic Four #45 (December 1965) and was created by writer Stan Lee and artist Jack Kirby. Within the Marvel Universe, Crystal is a member of a fictional subspecies of humanity known as Inhumans, who develop superhuman abilities when exposed to Terrigen Mist due to genetic modifications made by the Kree. The character possesses the ability to psionically control the four classical elements: earth, fire, air, and water and, by extension, various other natural materials and phenomena such as metals and electricity. Crystal was the first character to be identified as an Inhuman, and is one of the most prominent Inhuman characters. Crystal is a princess of the Inhuman Royal Family and sister of Medusa, Queen of the Inhumans. She often appears with her canine companion, Lockjaw. The character has regularly appeared as a main character in several comic book titles, including various incarnations of Inhumans as well as Fantastic Four and Avengers. The character is unique in her affiliation with all three of these groups. She is also associated, to a lesser extent, with the X-Men due to the character's previous marriage to Quicksilver, which resulted in their daughter, Luna.