The Warp Crystal is a faceted gem of an unknown crystalline material that shines. Originally, it was a delicate version of a silver-like material that he put an eraser on one end and at the other end a hollow tube, which could easily be plugged onto the blunt end of a pen. The filigree cage was provided with a door through which the crystal was taken out, and had the dimensions of four inches in length (about 10 cm) and 2/3 of an inch in diameter.
Some TMNT stuff was always meant for grownups.
The exact origin of the warp crystal and under what grounds had it appeared on earth, are unknown, but some hints are available in the comics that it came from the the world of Ebrik. The crystal was found by April O'Neil's father one day when he was a young man and was rummaging though second-hand goods in the warehouse in his shop for things that he could either sell or keep for himself. At the time his marriage was going though a crisis because his wife after the birth of his first daughter Robyn was no longer able to have more children, although she desired too.
Out of curiosity, O'Neil attached the crystal to one of his pencils and began to draw pictures. To his surprise, he quickly realized that the images actually became physical objects or living things, soon as the last line was completed. After he and his wife had been completely convinced of the power of the crystal, O'Neil tried to realize his wife's desire to have more children, but the babies created by the crystal dissolved into thin air after a short time. After some consideration, he had the idea, that the drawings were not staying because a pencil as a medium was not permanent. Therefore, he switched over to a ink pen, and indeed the new baby survived and grew up to be a hindrance adult.
However, April was searching for her past using the time guardian Renet's help and traveled in the past, and after - being in the body of a cockroach - had seen how she had come into the world, she and Renet one night took the crystal away from its socket and threw it down a drain grate in the basement of the house. The crystal landed on a coal pile and stayed there for many years undetected, until one day, April's new lodger, Kirby, found it and, in turn, used it to bring his drawings to life. The crystal finally was lost along with Kirby in Ebrik after he and Donatello helped the people living there against a horde of monsters. It's current whereabouts are unknown.
In the 2003 animated series, Kirby King and the crystal are used in the episode "The King", but the background story from the Mirage comics is never fully revealed. In addition, a short, probable allusion to April O'Neil's search for her past is made in the episode "Return of Savanti, Part 1".