The Warp (or Immaterium)

A ship leaving the warp

The Immaterium (also referred to Warp) is an alternate dimension of purely psychic energy that echoes and underlies the familiar four dimensions of the material universe. It is the source of all psychic powers and known instances of so-called "sorcery" and the home dimension of the Chaos Gods and their myriad daemonic servants. This function as a faster than light medium for travel is achieved by the Immaterium being a domain of pure psychic energy, with spacecraft navigating between currents, as in an ocean. The psychic energy that makes up the Immaterium is believed to be the direct result of the existence of sentience in the universe, in particular the Polaris Galaxy. Considered to be a dark reflection of the material universe, the Warp is an ocean of chaos, raw emotion given energetic form. Stirred by emotion and action, the Immaterium is the true realm of Chaos, home to the dark gods who comprise the Ruinous Powers and their daemonic followers. It also is rumoured to house the spirits of the dead, and therefore can be considered the "Underworld" of the universe.

Although being a useful way of travelling, the warp is no longer used, due the danger and slow velocity of travel. All new ships are no longer equipped with warp drives.

Warp Annomalies

A chaos death god from the warp

On rare occasions, the realm of the Immaterium is able to break out into the physical universe. These nightmare realms, known as Warp rifts, are usually home to the once-mortal followers of the Ruinous Powers of Chaos, and are often the site of titanic atrocities.