This ancient knight had the body of a humanoid insect with a multitude of hydra heads and three mouse tails. Yrsinius reigned for several aeons before suddenly disappearing. Some believe he was wandering into the chaotic depths of the Maelstrom when he fell victim to an ambush and was destroyed by a group of Proteans called the Chorus of Malignant Symmetry. If it still exists, however, the mighty Yrsinius could still return and claim his throne from Apollyon (a fact on which the current Pestilence knight often mulls over, since his kinship among the Four would be sidelined). From time to time, rumors emerge within Abaddon which speak of planar explorers who discover entire cities decimated by the plague in the depths of the Abyss, as well as stories of plagues that devour not only the flesh but also the soul, thus suggesting that Yrsinius may still be alive. Some have come up with a horrible concept that Yrsinius may have survived in some twisted, or chimeric, form rebuilt by the corrupt Proteans although they are responsible for his fall.