The Illyroi suite of mercenaries generates the following units:
- Illyrioi Machairaphoroi (sword levy)
- Illyrioi Peltastai (Mercenary Javelin Infantry)
- Illyrioi Hippeis (Mercenary Axe Cavalry)
All Illyrian units have a propensity for countering heavy infantry units, so the best way forward is to hose them with light infantry or ranged cavalry.
Beyond these, the Illyrian faction of Imperivm Invictvm also has the following as mainstream units:
- Phyletichoi Illyrioi  (Levy Spear Infantry)
- Hoplitai Illyrioi 
- Thureophoroi Illyrioi  (Javelin Infantry)
Historically, the Illyrians were a people that inhabited the northern part of modern day Albania and were bordered in the south by the Greeks of Eperios and Aitolia, and in the east by Makedonia and Thessalia. Thus, they had to adapt their warfare to fight these enemies, a task they became frighteningly good at. By the time of Philippos of Makedonia, they had carved out a fairly large kingdom at the expense of Makedones and Epeirotai. Philippos married Olympias of Epeiros and retook the Makedonian and Epeirote provinces for their respective owners, using Parmenion to take the Makedonian portion back. His son Alexanderos, a product of this marriage alliance against the Illyrians, attacked, subdued, and won over many of the Illyrian tribes. Fairly large contingents of his light infantry in the Persian conquest were of Illyrian extraction. They won their independence once more after Alexanderos’ death, but were never again to become a major power. The Illyrioi as a people were extinguished by the Romanaioi and Illyria became the first Roman province outside of the western Mediterranean. The Illyrians adapted quickly to Roman culture and became the first extremely loyal non-Italic subjects of the growing Empire.