OOOOOooohhh.
Now I see how this could be HUGELY impactful to SO MANY elements of the current canon. Pun unintended.
It's a cutscene, four completely soloable mini dungeons, and another cutscene before a boss that you have to wait 5 minutes on if you don't burst it to death instantly.
And then they reveal that was the First Coil... Sunovabish.
It's also a great way to fill up your basic tomestones real quick. Shit, I gotta spend these before I progress...