Time Stones

Time Stones (タイム·ストーンズ Taimusutōnzu?) are seven gemstones from the Little Planet which have power over time. They only have appeared inSonic the Hedgehog CD, in which they can be obtained from Special Stages, much like Chaos Emeralds in most of the other games.

The shape of Time Stones varies in two occasions. As it is shown in Special Stages and ending cinematic that gemstones have look of milled amethysts. But in the result screen after Special Stage, they are seen to look similar to Chaos Emeralds. The seven Time Stones are colored red, orange, yellow, green, blue, purple and cyan; similar to the colors of the Chaos Emeralds, except replacing white with orange.

Description
The Time Stones are a set of seven gemstones that has the power to control time, and allow their wielder to move through the passage of time. It is said that those who manage to possess all seven Time Stones can control all of time. It is implied, however, that the Time Stones cannot leave the Little Planet, or otherwise cannot be used elsewhere.

The Time Stones are found deep within Little Planet. They are able to transport the planet through time, and as such it is only visible in the planet's atmosphere for one month out of every year, above the Never Lake. In Sonic the Hedgehog CD, Doctor Eggman attempts to collect Time Stones in order to take over the Little Planet and the rest of the world. Sonic tries to stop his plans by finding them first.

In Sonic the Hedgehog CD, Time Stones can be collected from seven different Special Stages. To enter a Special Stage, the player has to collect more than fifty Rings and jump to the Giant Ring, which can found at the end of a round behind the signpost. In the Special Stage, the player has to destroy all of the UFOs. Collecting all Time Stones in the game unlocks the good ending of the game. In addition, anytime the player travels to the future in a zone, he/she will always travel to the good future, meaning that the player can enjoy seeing a beautiful stage landscape and not face any Badniks.

In the good ending of the game, Sonic collects all Time Stones, finally defeats Eggman in Metallic Madness and frees Little Planet from under Eggman's control as the planet transports with Time Stones in time from above of Never Lake. However in the bad ending, Eggman grabbed one of the Time Stones in his hand as he escaped from the Little planet.

Sonic the Comic
Time Stones also appeared in the British comic publication, Sonic the Comic. They were first mentioned in a Sonic's World back-up strip, in which it was revealed that there were six Time Stones rather than seven (at the time, the series also included only six Chaos Emeralds). The strip also mentioned that they were hidden somewhere on the Miracle Planet and that Doctor Robotnik wanted to find them so that he could control time and become unstoppable.

One such Time Stone appeared as part of a bizarre time paradox during the series adaptation of Sonic CD. Whereas the Time Stones that had appeared in the back-up strip appeared to be multi-coloured gemstones (as in Sonic CD), the one in the main story looked like a normal, oval-shaped grey stone, although it glowed when it was being used.

Robotnik had somehow located a Time Stone, and used it to power a machine that cyberformed the entire Miracle Planet in the space of a single month (between the planet's appearances over Mobius). Later, after Sonic had chased Metallix to the Miracle Planet in order to rescue Amy Rose, Sonic received the Time Stone from a duplicate version of himself from the future. He used it to travel back to a time before the planet had been cyberformed (although the Time Stone disappeared when he did so). He retrieved a past version of the Time Stone from Robotnik's machine (destroying the machine in the process), then travelled forward in time again to give the Stone to his past self (who then travelled back in time, as part of a closed loop). After Sonic's past version had left, the machine's effect on the Miracle Planet suddenly disappeared, as did Metallix.

Neither the Stone's origin, nor its eventual fate after its disappearance, were ever explained.

Sonic the Hedgehog (TV series)
In Sonic the Hedgehog animated series, there were two Time Stones. They were found on the Floating Island in a temple, and they could only be accessed by defeating the temple guards and answering the riddle asked by the Keeper of the Time Stones, an enormous, ancient owl.

Sonic and Princess Sally used these two Time Stones to transport themselves back to the day of Robotnik's takeover of Mobotropolis during the two-part episode "Blast to the Past" in an attempt to stop the takeover from ever happening. This ultimately failed as Sonic didn't keep his mind on the exact date, but Sally was able to download the original roboticizer plans from one of Robotnik's terminals and saved her nanny Rosie by telling her to never leave Knothole no matter what (due to the fact that Sally knew that she would be captured while out in the Great Forest and roboticized by Robotnik).

Archie Comics

 * Main article: Time Stones (Archie)

The Time Stomes is mentioned in the Archie Comics' Sonic the Hedgehog comic book series and spin-offs. In this media, much like in Sonic the Hedgehog CD, the Time Stones are hosted on the Little Planet, where they are rumored to be protected by Nicholas O'Tyme or the Knights of Kronos. One of them is used by Silver the Hedgehog and Mammoth Mogul to travel through time.

Trivia

 * Time Stones' similarity to the Chaos Emeralds is striking, in appearance as well as their ability to manipulate time and space. The only major change being that Time Stones are shown to be much larger, as Sonic grabs them after completing a Special Stage.
 * However there seems to be an inconsistency regarding its size, as its shown that Robotnik is holding single Time Stone in the ending cinematic, which is small enough to hold it in his hand.
 * The major difference between the Time Stones and Chaos Emeralds is that the Time Stones only seem to be able to warp through time on Little Planet itself.
 * Like Chaos Rings later in Knuckles' Chaotix, Time Stones cannot cause a transformation to its user.