Gachnar is the demon of fear that could be conjured by performing a summoning ritual using the Mark of Gachnar. Once the ritual begins, Gachnar's presence infects the reality of the immediate environment in which the ritual has been performed.
The effects of the infection range from (but are not limited to) transformations of inanimate objects to animate, temporary re-animation of corpses, temporary hallucinations affecting those in the area.
All of these effects are not only driven by the fear of the individual but this fear then "feeds" Gachnar who turns the fear into power which he uses to eventually bring himself forth, completing the summoning ritual.
The irony of Gachnar's title and nature is evident when one realizes he was merely inches in height.
Grachnar was portrayed by Adam Bitterman.