Kromaggs come from a world that followed a different evolutionary path. They communicate telepathically with one another though they do have the power of distinct speech.
Kromagg Prime, where cities are built into gigantic trees, was once a hellish place where tribal wars were endless until the discovery of sliding. When they ventured into the vortex they were shocked to find other worlds where humans had developed rather than species such as their selves. This frightened them and the “people” of their world banded together to fight a now common enemy — humans. To do this, they created a single, military government that dedicated itself to traveling to other worlds, via sliding, in order to eradicate all of the human races encountered. As a result of the endeavor, the civil wars ceased.
This so-called Kromagg Dynasty has been invading worlds for 20 years and their conquests have always been successful. When the Kromaggs conquer an earth, they kill most of the humans while saving others for slave labor or food… it seems they have an appetite for human eyes. When they take humans with them, they are first brought to Outpost Earth 113 where they are kept in prisons until such time that they would be brought along to the Kromagg Prime, probably for further study.