A precursor to a Tyranid hive fleet’s arrival is the so called Mahir Leaper, a Gaunt genus variant found on the death world of Mahir. The Mahir Leaper is believed to be derived from Gaunt specimens that arrived on the planet in Mycetic Spores or even possibly aboard a crashed Hive Ship.
The creatures have adapted to local conditions by becoming smaller and more agile, compensating for their lessened strength with increased numbers and a hardened carapace. A hunting pack of Mahir Leapers can be up to sixty strong and well able to take down the largest prey. The Xenos Bestiarium, on Watch Fortress Erioch, maintains a substantial breeding stock of Mahir Leapers for use in the Hunting Grounds. Battle-Brothers find that the fast moving, hard-shelled leapers make for excellent target practice.