Wow.

Make sure you take it into New Game+.
The Rood Inverse doors don’t open until you have the Tattoo, and Most of the game is THERE.  (I still have my playthrough 7 save.)

Perfect explanation.

https://www.ruindays.com/collections/all
I’ll bet this is where they came from.

What about Millhouse Manastorm? He’s sort of a hero, isn’t he?