Akth'tjak is the Klack version of Hell. In Klack mythology it is a Black Nest where all evil and bad Klack go who have done wrong (The only Crime Klack know is to oppose the will of the Queen. It is considered a sin to even think anything negative about the queen. In a society that evolved from a common shared nest intelligence, feelings and strong thoughts are still shared, such thoughts are the same thing as actually committing a crime.
The Unspeakable Demons that rule the Black nest are described as eight legged and is described pretty much exactly like Archa look.
Klack are among the bravest and most fearless warriors but the sight of an Archa puts them in panic and fear.