Although the X'i race seems unwilling to divulge their history to organic historians such as us, expeditions into abandoned territory allow us to explore and estimate based on texts left behind. One large abandoned city filled to the brim with mounds of solidified graphite had an unusual journal left behind that appears to mention some sort of enormous underground monster that fed on X'i and other supposed 'entities'.
There was a poor sketch of it, and the only recognizable feature of the animal was a head somehow resembling a Platybelodons from Earth. According to the journal, it used thousands of strawlike tongues to drink the radioactive energy straight out of its prey.
It may also be the culprit behind the mounds of solidified graphite. Of course, there is always the possibility that the graphite mounds are fossilized X'i ancestors. We'll likely know, once we learn how to comprehend the structure of the X'i...and they aren't helpful in this regard.
