Doctor Eggman Nega's camera

Doctor Eggman Nega's Camera is the primary plot device that drives the story in Sonic Rivals. While appearing as a normal camera, it is actually a highly advanced piece technology from approximately 200 years into the future. Any object that this camera takes a picture off will instantly be converted into a card.

In Sonic Rivals, Eggman Nega master plan was to use this camera to alter his family's history by erasing his ancestor Dr. Eggman and his failures from the world so that his brilliance would be recognized in the future. He was however stopped by Sonic the Hedgehog, Knuckles the Echidna, Shadow the Hedgehog and Silver the Hedgehog.

Description
On the front, Dr. Eggman Nega's camera appears as a regular, multicolored digical camera, which only serve to cover for this device's more dastardling properties. Any target that the user choses to take a picture off with this this camera, be it either inanimate objects or living beings, will then be converted an into inanimate, two-dimensional card.

Living beings that are turned into cards by this camera are seemly locked in some kind of stasis while ony being semi-aware of the happenings around them while in card form. Objects with certain properties, such as the Master Emerald, that are turned into a card by this camera, allows the holder of such cards to manipulate the properties of the said object as the holder desires.

While it has not been explained how objects captured by Dr. Eggman Nega's camera can be freed from the cards and returned to normal, it appears that the conversion happens independently and according to the holder of the cards' will; when Sonic acquired Tails and Amy cards, he was seemingly able to return them to normal in the following cutscene.

History
Created at some point in Silver's future thanks to this era's advanced technology, it is unknown whether this camera was one of Doctor Eggman Nega's own creations or that the doctor stole it from somewhere (though Silver's statements might confirm the latter). Having his genius and honor of coming from a lineage of brilliant scientists denied due to the historic failures of his ancestor Dr. Eggman, Eggman Nega acquired this camera and decided to change his family's history by using the camera to trap the present-day Dr. Eggman inside a card, thus allowing Eggman Nega to take control of his own destiny.

Prior to events of Sonic Rivals, Dr. Eggman Nega used his camera to photograph the Master Emerald in this time, trapping it in a card so that he could use its awesome powers for his own purposes; however, due to the Master Emerald existing simultaneously across the time-space continuum, this act resulted in the Master Emerald disappearing in all time lines as well, even in front of Knuckles the Echidna's eyes in the present as well. Eggman Nega then used the Master Emerald card to teleport Onyx Island to Sonic's time to serve as his vehicle through the time stream. Silver the Hedgehog, however, learned of Eggman Nega's use of the camera, and followed the doctor into the past to prevent Eggman Nega from using the camera's power to wreak havoc.

In Sonic's time, Dr. Eggman Nega did not waste any time and began to use his camera to turn various other objects to cards as well. When Miles "Tails" Prower, Amy Rose and Rouge the Bat later arrived at Onyx Island, Eggman Nega turned them into cards as well with his camera, to keep them from meddling in his plans, before finally succeeding in capturing his target, Dr. Eggman in a card with his camera as well.

Of the course of the game, Eggman Nega suffered several defeats and setbacks at the hands of Sonic the hedgehog, Knuckles the Echidna, Shadow the Hedgehog and Silver the Hedgehog, Eventually, Eggman Nega finally snapped, going into a insane frenzy and decided to turn the entire Earth into a card with his camera; while it would endanger Eggman Nega existence as well, Eggman Nega cared not as if he could have the future, then no one could. Escaping to the Meteor Base Zone, Eggman Nega mounted his camera to his spaceship, the Egg Destroyer, and planned to charge the camera with the cards containing Amy, Rouge and the Master Emerald. As Eggman Nega took off in the Egg Destroyer to go through with his insane plan, however, Sonic, Knuckles, Shadow and Silver managed to stop the doctor's vessel, causing Eggman Nega to lose control of the camera and got turned into a card himself, while the heroes managed to free all Eggman Nega captives in the cards.

What happen to Doctor Eggman Nega's camera afterwards is unknown; either it was destroyed during the final battle or it was reclaimed by Silver, who took it back to the future.

Trivia

 * The camera provides an in-story rationale for the collectable cards that are picked up over the course of Sonic Rivals.