Ratlings are the smallest of the Imperium's known abhumans, catalogued as Homo sapiens minimus. Their ancestors dwelt on bountiful, gentle worlds richer even than ancient Terra, and across thousands of years of easy living and inbreeding the stock grew stunted, short and squat, and far weaker than a baseline human. Their principal homeworld is Ornsworld in the Segmentum Obscurus.
By temperament they are idle, greedy and hedonistic, forever eating, drinking and making mischief, and their fondness for pilfering and slipping away from danger has earned them the deep distrust of the ordinary soldiery. Yet the Imperium suffers their vices for one reason above all: no abhuman shoots straighter.
Ratlings are natural marksmen of uncanny ability, and it is said a Ratling sniper can take the head from a heretic at better than a kilometre's distance. Their tiny frames and light weight lend them a real gift for concealment, letting them find firing positions others could never reach and stay out of harm's way once the shooting begins. Deployed as sniper auxiliaries, they melt into cover and thin the enemy ranks from afar, killing officers, specialists and champions with patient, unhurried precision while the great battle rages on without them.