Darkspine Sonic

Darkspine Sonic (ダークスパインソニック) is one of Sonic the Hedgehog's transformations, appearing in Sonic and the Secret Rings. Rather than using the Chaos Emeralds, he uses the World Rings of rage, hatred and sadness to transform. In this form, Sonic's personality is slightly more sinister and violent due to the intense feelings that each of the World Rings contain. He is playable in the final battle against Alf Layla wa-Layla, an enhanced form of Erazor Djinn.

Appearance
In this form, Sonic's fur and his arms become an indigo blue and his quills hang lower than usual. He gains four golden rings, two on his wrists and two on his ankles. Also, his gloves disappear and his feet have turned indigo with a white stripe across each of them (indicating his shoes have either disappeared or changed to match his fur). Two white vertical lines come down from the middle of his forehead and runs up his upper and lower middle quill, and one white, wide line runs across each of his feet. His skin turns pale white, and both his irises and pupils disappear. Also, his voice has a slight change, becoming more demonic, but maintaining Sonic's pitch. He is also constantly surrounded in a flaming aura.

Powers and abilities
In this form, Sonic has increased physical strength, enough to send Alf Layla wa-Layla's strongest attack back at him with brute force alone. He is also granted the ability to fly through midair and can move at high speeds through midair.

As Darkspine Sonic, Sonic is granted pyrokinetic abilities, allowing him to control fire, though it is not shown to what extent. As seen in his battle with Alf Layla wa-Layla, Darkspine Sonic can create concentrated flames on his hands and feet to amplify the destructive effect behind his attacks and form highly powerful bursts of flames when hitting his opponent. His attacks are also more close-combat based, as opposed to the boosting and energy moves that Super Sonic uses.

Besides physical abilities, Darkspine Sonic is able to perform his ring powers Time Break and Speed Break on his own, without the need of Shahra's ring itself. He does not lose rings gradually like Super Sonic, but he can lose rings from being hit. His Soul Gauge and Ring Counter are upgraded to the maximum, and he is able to fill up his Soul Gauge by spinning around in a manner similar to his Spin Dash.

As the World Rings are what keep the world of the Arabian Nights together, it appears that Darkspine Sonic is capable of warping the reality of the Arabian Nights' universe; with but a flick of his wrist, Sonic was able to revert Erazor Djinn's apocalyptic world - and himself - back to normal.

Trivia

 * Darkspine Sonic is one of three transformations Sonic has undergone that were unintentional, the other two being Sonic the Werehog and the similar one, Excalibur Sonic.
 * Darkspine Sonic can be considered the second form of Sonic that was not attained using Chaos Emeralds.
 * It can be believed that Darkspine Sonic is an incomplete transformation, as he only used three of the seven World Rings. Thus, it can only be assumed that by using all seven World Rings, Darkspine Sonic will be at his strongest (it can be assumed that he might even gain invincibility, as it would parallel his real world reaction with all seven Chaos Emeralds).
 * It is believed that Darkspine Sonic's pyrokinetic powers were inspired both by the fact that the original title of the game was intended to be 'Sonic Wildfire' and the recurring use of fire based techniques by Sonic in-game.
 * In Mario & Sonic at the London 2012 Olympic Games, the answer to one of the Shy Guy's questions that concerned Darkspines was that 'Darkspines controlled fire'.
 * Darkspine Sonic's voice seems may have been the inspiration for the voice of Sonic the Werehog in Sonic Unleashed, as both their angry speech patterns and gruff vocal characteristics are strikingly similar. His voice also sounds similar to Jet the Hawk at times. This is no surprise, seeing as they all have the same voice actor.
 * When transforming, Sonic was shown to be in an amount of pain, making this the first time in the games that Sonic has ever dealt with negative side effects whilst undergoing a transformation.
 * Despite this transformation being made out of negative emotions, Sonic seems to maintain relatively his typical attitude. An example of this is when he says to Alf Layla wa-Layla "HA! How's that for an introduction?" Despite this, he is shown to be undoubtedly much more reckless and ruthless in combat.
 * This is the first form in which Sonic seems to have neither gloves nor shoes, and possibly the only time he has ever been seen without said articles of clothing.