Interaction with the Physical World
The Warp is notable for being influenced by the minds of most sapient beings. This interaction ranges from subtle effects of conscious or subconscious thought inside the Warp to conscious manipulation of Warp energies as psionic powers. This interaction is also harmful, however, as powerful emotions from large groups of individuals can give rise to entities inside the warp, generally referred to as daemons.
The most common use of the Warp by the various races of the Milky Way galaxy is FTL travel. Warp travel is the basic form of FTL travel in the WH40K universe, but it has numerous problems. The Warp is an unstable place and is filled with various hazards, including warp storms and daemons. To navigate in the Warp, the Imperium created the Astronomican as a psionic beacon, which psychic navigators can see and use as a reference point. To protect the crews of spacecraft from the threats of warp travel, Imperial starships employ a device known as a Gellar Field.