Chaotic Inferno Zone
From Sonic Retro
Chaotic Inferno Zone is the sixth and final level of Sonic Rivals 2 for the PSP. An incinerated dimension inhabited by the Ifrit, the Zone oddly contains only Acts 1 and 3 plus a boss fight at the end; except for Shadow and Metal Sonic, who do get an Act 2 in the form of a knockout battle against Metal Sonic 3.0.
Bearing suspicious resemblance to Sonic '06's Crisis City, Chaotic Inferno Zone is an entire world which has already fallen to the Ifrit's flames. Smoldering husks of buildings, seas of lava, rusted grind rails, and flame cyclones all play ruined testament to the Ifrit's pyrotechnic power. The zone also features rocket-riding segments, required to ascend the rocky chasms which the characters encounter.
Cut off from the Doctor's transmissions in Mystic Haunt Zone, Shadow incorrectly inferred that Rouge was entering the mansion to find the final Chaos Emerald. However, unbeknownst to the black hedgehog, the seventh gem was in fact hidden inside Metal Sonic. By pursuing Rouge to Eggman Nega, Metal Sonic and Shadow were eventually responsible for bringing the gems close enough to open the dimensional doorway, and allow access to Chaotic Inferno. Nega, though surprised by his unexpected success, swiftly orders his own version of Metal Sonic, the black-and-yellow 3.0, into the portal to retrieve the Ifrit. The real Eggman then appears, informing Shadow that his grandfather's notes indicate that it's possible to close the portal from the inside. Shadow and Metal Sonic proceed to dive in, to stop 3.0 and seal off the dimensional doorway.
Sonic and Tails, having freed the chao from Nega's secret room, dive in under the same premise. Knuckles (for once in the game capable of seeing beyond his duties as Guardian) follows suit, dragging Rouge with him (despite her loud displeasure at being forced into acts of unpaid heroism). Silver and Espio, having failed to find the chao on account of Sonic's faster rescuing, believe that their quest is failed; but on realizing that 3.0 has to actually reach the Ifrit in order to awaken it, decide there's still a glimmer of hope and enter the portal too.