From Sonic Retro
Perhaps due to Shadow and Sonic's total xenocide in downtown Westopolis, Black Doom decides to get out of town after acquiring a third Chaos Emerald, demanding that Shadow accompany him with the other two emeralds thus collected. Sonic, however, wants Shadow's help again, this time to destroy the Black Tank.
Obediently follow Black Doom and Shadow will warp to the next stop in his whirlwind adventure, Prison Island. Destroy his precious Black Tank, however, and Black Doom will become pissed (for the first of possibly many, many times) and summon Black Bull to charboil Westopolis and Shadow. Beat Black Bull and Shadow will tend wander about searching for that damn fourth Chaos Emerald for a bit before stumbling upon Circus Park.
A highway in the sky, Leathal Highway is crawling with Black Warriors, Black Larve and Black Hawks. There are also many scattered bombs that detonate and destroy sections of the road when approached, and Dark Spin Dash slime covering portions of the stage. Like Westopolis, the level is in ruins, with many destroyed roads and cars strewn about. Some of the broken debris and roadside fixtures can be utilized as melee weapons. In the background are advertisements for diamond rings, a car called "Control Chaos" (Chaos Control backwards), and the NiGHTS into Dreams hotel (seen in Radical Highway). The vehicles Shadow can find in this stage are SUVs and motorbikes.
- Hero: Sonic the Hedgehog: Mission: Destroy the Black Tank!
- Dark: Black Doom: Mission: Escape from Westopolis.
The boss of Lethal Highway is a giant monster called Black Bull.