The Scinfaxi (シンファクシ Shinfakushi) was the first Scinfaxi-class nuclear submarine developed by the Union of Yuktobanian Republics during the Cold War. It along with its sister ship, the Hrimfaxi, was later destroyed during the Circum-Pacific War.
After the submarine's unveiling in early September 1991, the Scinfaxi entered service with the Yuktobanian Navy; however, the vessel's battle record prior to the Circum-Pacific War in late 2010 remains unknown.
On September 30, 2010, the Scinfaxi deployed its fighter aircraft to perform air strikes against the 3rd Osean Naval Fleet as it passed through the Eaglin Straits. The Yuktobanian fighters were intercepted by OADF escorts, prompting the Scinfaxi to launch a salvo of burst-missiles at the fleet. The resulting detonations were incredibly destructive: the Scinfaxi successfully sank two of Osean fleet's three aircraft carriers and virtually wiped out all of the Oseans' carrier-launched escort fighters. At some point after the engagement, the Scinfaxi began heading towards Osea's easternmost outpost, Sand Island.
On October 4, Yuktobania attempted an amphibious assault and invasion of Osea's Sand Island Air Force Base, from which it would begin an invasion of the Osean mainland. The Scinfaxi spearheaded the assault and began firing burst-missile barrages at the Osean defense squadrons. However, Scinfaxi's burst missiles began to be intercepted by the Arkbird's recently acquired laser cannon before they could detonate.
To compensate, the Scinfaxi fired several burst missiles in quick succession to prevent the Arkbird from destroying all of the warheads. The explosions annihilated a majority of the Osean pilots except Wardog Squadron. The Scinfaxi's underwater SLBM launches allowed the Oseans to use sonobuoy data to isolate the submarine's location. It was subsequently targeted and hit by the Arkbird's orbital laser, forcing the Scinfaxi to surface. Upon surfacing, the submersible defended itself with carrier-launched and VTOL aircraft, surface-to-air weaponry, and burst missiles as the Wardog Squadron attempted to destroy it.
The Scinfaxi eventually lost its defensive weapons, and the Arkbird fired its laser once more into the submarine, preventing it from launching more aircraft. Wardog Squadron then dealt the final blow and sunk it; shortly after, the Scinfaxi's nuclear reactor went critical, causing the vessel to be torn apart from the inside.
- The names of the Scinfaxi and its sister ship, the Hrimfaxi, are taken from Norse mythology: Skinfaxi and Hrímfaxi are the supernatural horses of Dagr (god of day) and Nótt (goddess of night), respectively.