Can anyone explain what “The First” even is? Or it’s significance?

[Schan]

frankly, I find this game’s MSQ very uninteresting and boring. (...) I hear people freaking out about “The First” this, or “The First” that. (...) I usually don’t care about MSQ.

Maybe I'm reading "freaking out" with an overtly negative connotation, I don't know.