The Yull are man-sized, allegedly intelligent beings descended from something very much like a lemming. The lemming men follow a strict martial code that requires its adherents to embrace death, especially if at the top of a long drop.
The war-god of the lemming men has declared that only one species shall rule the galaxy, and to everybody’s surprise it has picked the lemming men to do it. The Yull regard all other sentient beings as cowardly, and believe that their Divine Migration will bring them limitless territory and sacrifices for their savage deity. Considering all other lifeforms to be worthless insects, they have formed a somewhat illogical alliance with the worthless insects of the Ghast Empire.
The average Yull is a vicious, irascible lunatic with absolutely no interest in his own safety, whose depraved outlook ranges from frenzied rage to raging frenzy. When not grovelling before his masters he is usually to be found sharpening his axe or running screaming at either an enemy or a cliff. The Yull are not to be underestimated, as several of our planets have already found out. Stern measures need to be taken: the Deepspace Operations Group has been informed.