Ytarrans

The Ytarrans were a race of Gnome-like humanoids who inhabited the nation of Ytarra until a few centuries before the present day. Their inquisitive nature endeared them to Ytaru, who lived among them as a god (as opposed to incarnating as a mortal) and progressed their technology to such a degree that it is advanced by our real-world standards, in a setting that is otherwise Medieval fantasy.

The Astral Plague
The Astral Plague (AKA spell plague) is a condition caused by exposure to Astral Energy. it appears to have more in common with radiation sickness, or perhaps cancer. It is best known for wiping out the Ytaran civilization.

Effects

Those afflicted with Astral Plague are forced to make regular con saves. On failure, the afflicted fades from existence. Without treatment, this is of course fatal.

Known Ytarrans
Y'Solas Turi

Yttronium
Yttronium is a blue metal created by Ytaran creation matrices. Metallurgically, it is similar to steel, with a higher tensile strength but other drawbacks to cancel this out. In terms of pure game mechanics, it's steel.

Creation Matrix
Creation matrices were devices created by the Ytaran Empire to aid in construction.

One was stolen by a dragon toward the end of the Ytaran empire

One was buried with Y'Solas Turi.

It is unknown whether any other matrices exist, but it is unlikely.