Triton is the largest natural satellite of the planet Neptune, and was the first Neptunian moon to be discovered. Triton has a surface of mostly frozen nitrogen, water-ice crust, an icy mantle and a substantial core of rock and metal.
Triton has a tenuous nitrogen atmosphere, with trace amounts of carbon monoxide and small amounts of methane near its surface allowing high resilience form of exobiology to grow below its surface.
Miles below the frozen surface and deep within the underground caves of this extreme hostile environment is the home of the Triton Black Dragon which thrive in the relatively warm and moist underground environment.
The Black Dragon blooms three times per Earth year...