WoL Spirit mode "Ruins"

[XDaDePsak]

I've encountered the Ruins in spirit mode, where you apparently let 4 of your spirits just wander on their own, autonomously for 2 hours.

I can't find any information about this thing. Is there only 1 ruins, are there multiple ones? What's in them? Anything worth it?

A general guide would be nice but I can't find anything about this feature.

 

[Kholdstare]

There are caves near the south side of the map that do the same thing, except for six hours. They only give items to help with spirit battles, not any currency or extra spirits.

 

[JiggyNinja]

There's another one on the right side of the map that takes 10 hours. I hear it mostly gives candies.