Thank you so much for taking the time to explain everything!
It makes a lot more sense now. I really like the idea that the Echoes are benevolent remnants of people still attached to artifacts, and that Harmonizers must resonate with them to safely recover those relics. That's a really evocative concept, and I think it will come across much more clearly once you expand that part of the lore.
The Challenge Pool explanation also cleared up my confusion immediately. I think a gameplay example will make it click for future readers.
I'm really looking forward to reading the post-jam version. I think the foundations are already very strong, and with a few more examples and a little more lore, it will be even easier to immerse yourself in your world.
Thanks again, and good luck with the post-jam update! 😊