Calth
From Lexicanum
| Map | Basic Data | Planetary Image | |
| Name: | Calth | 
|
| Segmentum: | Ultima Segmentum | ||
| Sector: | Unknown | ||
| Subsector: | Unknown | ||
| System: | Unknown | ||
| Population: | Unknown | ||
| Affiliation: | Imperium | ||
| Class: | Civilized World | ||
| Tithe Grade: | Unknown | ||
Calth is part of Ultramar, the Ultramarines Empire, and one of its most productive worlds. It is an airless world, and its surface is uninhabitable due to the deadly light of its blue sun. Calth's population lives in massive underground cavern-cities. The planet is known for its orbital shipyards, which provide the craft used by the Ultramarines, as well as civil and military craft for wider use in the Imperium. The planet is also the birth place of the exiled Ultramarine Uriel Ventris
During the Horus Heresy, Calth was used by Roboute Guilliman as a staging point for his supposed assault on the Veridan System. Horus had ordered the Ultramarines there to divert them from the Siege of Terra. It was then that they were attacked by a force of the Word Bearers legion.
Calth has escaped attacks by both Hive Fleet Behemoth and Kraken.
