This year Audi Sport celebrates 25 years of RS high-performance models with a special exhibition at the Audi Forum in Neckarsulm, Germany.

To date, the division formerly known as Quattro GmbH has launched a total of 25 RS models, beginning with the RS2 Avant in 1994. Besides the familiar production models, the exhibition that opened on July 12 also includes a total of 14 “genuine RS rarities.” Those include a racing version of the Audi TT RS from 2011 developed for the Nürburgring 24 Hours, an RS5 DTM racer that won the 2013 season, and an Audi RS8 prototype that never reached production.

Obviously, the latter car caught our attention and we managed to find some photos of it on Audi Forum Neckarsulm’s Facebook page. The caption does not offer too many details about this one-off creation built in 2013 that was supposed to sit above the S8 as the ultimate Audi A8 variant money could buy.

Based on the third-generation Audi S8, the RS8 featured a more menacing look courtesy of wider wheel arches, a new front bumper with massive air intakes, a gloss black grille featuring a honeycomb mesh and adaptive cruise control sensors at the top, and unique headlights that look like a combination between those of the A8, A7, and A6.

Other RS-specific details include the carbon fiber mirror caps and front bumper blades, as well as the massive dual-tone RS wheels shod with Pirelli performance tires. Stopping power was ensured by ceramic brakes featuring distinctive orange calipers. We’re sure that massive oval tailpipes and a diffuser are also part of the package but we haven’t found a photo of the rear end yet.

Inside, you can see a brand new flat-bottomed steering wheel wrapped in Alcantara using orange stitching, carbon fiber trim on the dash, center console, door panels, and redesigned transmission lever, as well as a Lamborghini-style start/stop switch. The rotary control for the MMI is nowhere to be seen, though — at least in the only interior photo we have.

There are no details regarding the powertrain but the S8 that Audi Sport engineers used as a basis for this prototype featured a 4.0-liter twin-turbocharged V8 gasoline engine that made 520 PS (513 hp) and 650 Nm (479 lb-ft) of torque. Given the RS8 moniker, we figure Audi must have squeezed even more power from the eight-cylinder engine.

Also read: 2020 Audi S8 Unveiled With 563 hp, Twin-Turbo V8

The Audi RS7 Sportback launched in 2013 featured 560 PS (553 hp) and 700 Nm (516 lb-ft) of torque from essentially the same engine so the RS8 probably offers similar figures. Audi does not say why the RS8 didn’t make it to production but that probably had something to do with the S8 being fast and powerful enough and the RS7 Sportback too close for comfort when it came to pricing and performance.