Tanith
Tanith was an agri/hive world in the Imperium of Man, home to vast forests of nalwood trees. Nalwood trees were able to move themselves around, creating a forest where paths were meaningless. This created a population of men who had almost superhuman spatial awareness and could find their way anywhere. These men were also Scottish Ninjas using their hunting abilities and stealth cloaks to become basically invisible. Tanith and its troops appear in the Gaunt's Ghosts series, written by God Himself.
The capital city of Tanith - surrounded by a giant wall, presumably to keep the nalwood trees from moving into the city - was Tanith Magna. The world was governed by the Elector, and the main governmental building was the Assembly. The planet was split up into counties, and each city raised a militia, from which a number of Imperial Guardsmen were recruited.
Tanith's native wildlife include larisel, small animals hunted by woodsmen - presumably for food - and shoggy, small amphibian creatures with bulging eyes that dwelled by woodland pools in Tanith's forests.
Destruction of Tanith
"It all went wrong on that very last night. Embarkation had already begun. Most of the troops were either aboard transports waiting for take-off or were heading up into orbit already. The navy's picket duty had not done its job, and a significantly-sized Chaos fleet, a splinter of a larger fleet running scared since the last defeat the Imperium Navy had inflicted, slipped into the Tanith system past the blockades. There was very little warning. The forces of Darkness attacked my homeworld and erased it from the galactic records in the space of one night."
- – Caffran, a member of the Tanith First and Only, relating the destruction of Tanith.
Tanith was destroyed by Chaos right at the end of a founding of the Imperial Guard, leaving only the Tanith 1st alive. Thus their nickname as the Tanith First and Only. The Chaos armada bombarded Tanith from orbit, and deployed ground troops to kill vital Imperial personnel before burning Tanith and its forests with the fleet's firepower. Seeing as the entire command structure of the Tanith troops was destroyed, Colonel-Commissar Ibram Gaunt was assigned to take command of them. The Tanith were promised a new world during the Sabbat Worlds Campaign, but were not given one (yet).