Iriil is a mysterious substance which is only found orbiting, at high velocity, the largest black holes. It's theorized to exist in the hearts of the hottest stars as well, but for obvious reasons nobody can confirm this. What iriil is isn't known - it doesn't appear to fit any of the known forms of matter (gas, liquid, solid, plasma), and appears to sometimes have properties of all of those four simultaneously. What we are certain about, however, is iriil's strong connection to kith. Unlike astrium, which is believed to be a byproduct of iriil decay, iriil appears to have a direct connection to kith, and we are fairly certain that it's the result of the destruction of the Empyreal Omega during the Worldbreaking.