Looking for some clarifications on new reveries in the rain

So I've been busy this past month and have pretty much only done the bare minimum content to get pulls, I've kept dismissing the pop-up that talks about the new reverie support system and finally decided to click on it just today.
I realized the biweekly content that fueled my euphorias is gone and is now been replaced with the nightmare lair which I'm guessing is like a tower system?
My question would be what exactly changed here? How do I farm euphorias now? How deep does this new content go? Am I supposed to clear this once a version or something?
Any input is helpful.
Any kind of summary is appreciated.