(Manticore A-IV)
Sphinx from space.png

Manticore-A System


Star Empire of Manticore


15th Century PD


Yawata Crossing (original)


1.2 billion humans[1]
~ 12 million treecats


13,906 km


1.35 G




Sphinx, also called Manticore A-IV, was one of the three inhabited planets of the Manticore System, and the homeworld of the treecats. It orbited the system's primary star along with the planet Manticore.

Star geography[]

Sphinx was located further away from its star than Manticore. As a result, the climate was on the cooler side of Terran norm. Also due to its higher orbital radius, the Sphinxian year was roughly five times as long as Earth's year, with a corresponding increase in the length of the seasons. The planet's gravity was 1.35 times as high as Earth's.

Sphinx days were 25.62 T-hours long, and there were 1,783.28 days in a Sphinxian Year. There were 1,903.65 T-days in a year, and one Sphinx year equalled 5.22 T-years. The Sphinx year was divided into 46 months, 35 of 39 days and 11 of 38 days. The shorter months fell into even-numbered months from 12th month to 32nd month, with a leap year every seven years. Sphinx had a fourteen-degree axial tilt. (UHH)

Planetary geography and climate[]

The planet had several continents, including Haley's Land, Thule, and Justianna. (infodump) Eighty percent of the land surface was covered in forest. (SK2)

Sphinx icebergs were proverbially unapproachable. (HH1)

Sphinx had particularly cold winters. (HH2) The Tannerman Ocean was a large body of water located on the planet. The Copperwalls were a mountain range. Because of the planet's distance from Manticore's sun, the planet had a very active carbon dioxide cycle that helped maintain the atmosphere and environment. (HH3)

The atmosphere was composed of 83 percent nitrogen, 15 percent oxygen, 1 percent argon, and 1 percent carbon dioxide, making it breathable for humans. (infodump)


On January 3rd, 1519 PD, the discovery of the twelfth sentient species known to man took place, as did the first bonding of a human and a treecat. (HHA1.1: ABF)

In 1568 PD, following ratification of the Ninth Amendment to the Manticoran constitution, treecats were given basic rights under Manticoran law, and one-third of the land on Sphinx was protected as treecat habitat in perpetuity.

In 1652 PD, Crown Princess Adrienne went on a state visit to the planet and survived an assaination attempt, shortly after being adopted by a treecat. (HHA2.2: WPD)

In 1859 PD, Honor Harrington was born on the planet. (UHH) In 1874 PD, Harrington left the planet for Saganami Island. (HH3)

In 1903 PD, HMS Fearless went to Vulcan for a refit and overhaul. (HH2) In 1904 PD, Harrington visited the planet while on vacation. She vacationed on the shores of the Tannerman Ocean. (HH3)

In February 1922 PD, the space station Vulcan was completely destroyed by the Mesan Alignment Navy as part of Operation Oyster Bay. Debris from the station rained down onto the surface of Sphinx, destroying the city of Yawata Crossing, damaging many other habitats, and wiping out the Black Rock Clan of treecats save for one survivor. (HH12)


Treecats were a sentient species native to the planet. The rabbit adapted to Sphinx's environment very well after being introduced by human settlers. (HH2) Some of the native plant life are crown oak and picket wood which grow on the lower elevations. (HH3)

The sabrepike was a native species of predatory fish. (HH8) Native land animals included the hexapuma, the Peak bear, the near-beaver, and the wood rat. (HHA1.1: ABF, infodump)

The aerial fauna included four-winged bird equivalents as well as the mammalian condor owl. (infodump)

Notable Natives[]


  1. As of 1920 PD