From 1d4chan

The Segmentum Fortress of Segmentum Tempestus and thus headquarters of Battlefleet Tempestus. The Segmentum Fortress consists of a massive number of stations and shipyards orbiting the planet. Bakka is a hellish young world, inhospitable even compared to forge worlds but rich in minerals. The surface is mainly a bunch of basalt and granite rock "islands" in a sea of lava and other hot stuff with a smokey atmosphere choked by poisonous fumes. All in all, it's basically the planet Mustafar from Star Wars ripped wholesale, as expected of Geedubs.

Bakka was the site of the Gareox Incident in M36, which led to the Imperial Navy's current distaste for carriers. Battlefleet Tempestus became divided into a traditionalist faction and a pro-carriers faction (which happened to be full of chaos cultists). A space battle ensued which went poorly for the carriers until they went openly traitor and fled.

Also briefly rebelled against the Imperium during the Plague of Unbelief before being purged by the Spess Furries.

The Red Corsairs attacked the shipyards at the closing of the 41st Millennium in search of new rides to loot. They were repelled by a force of Grey Knights who tried and failed to take Huron Blackheart's head.

Yet AGAIN, they were raided by the Dark Eldar of the Kabal of the Black Heart, but the purpose of the raid was not to steal inferior mon'keigh ships, but to instead serve as a diversion for Vect to kidnap a bunch of Nulls from an inquisitorial facility hidden on the third moon of Bakka.

N-not that it likes you or anything... idiot!

The Planets, Systems, Regions and Sectors of the Galaxy
Imperial Homeworlds: Holy Terra - Sacred Mars
Primarch Homeworlds: Baal - Barbarus - Caliban - Chemos - Chogoris - Colchis
Cthonia - Deliverance - Fenris - Inwit - Medusa - Nostramo
Nocturne - Nuceria - Olympia - Prospero - Macragge
Notable Imperial Worlds: Armageddon - Bakka - Cadia - Catachan - Cretacia - Ganymede
Hydraphur - Necromunda - Krieg - Kronus - Phyrr - Pythos - Sacris
Sanctuary 101 - Scelus - Scintilla - Tanith - Tartarus - Titan - Vigilus
Vraks - Zayth - 108/Beta-Kalapus-9.2
Daemon Worlds: Bathamor - Black Marble - Fleshworld - Glass Moon
Medrengard - Plague Planet - Sortiarius - Sicarus
Systems and Regions: Ghoul Stars - Halo Zone - Jericho Reach
Kaurava System - Solar System - Stygius Sector
T'au Septs - Taelus System - Ultramar
Types of Worlds: Agri-World - Craftworld - Daemon World - Death World - Eldar World
Forge World - Fortress World - Hive World - Civilised World - Tomb World