I saw a video on instagram where they mixed candy melts and marshmallows together. It made almost a clay. I've never seen this before. Does anyone have a recipe? Does it harden eventually? Thanks!

https://instagram.com/p/BSCVvt5gNQw/

It's a variation on marshmallow fondant/candy clay.  The candy melts will make it stiffer than straight MMF, but it won't be as stiff as straight candy clay.

https://www.facebook.com/notes/sweetn-simple-cakes-by-amelia/candy-melt-marshmallow-fondant/410763982277166/

I also saw this yesterday.  Haven't tried it, but it seems simple enough.

https://www.facebook.com/FirstMediaBlossom/videos/10155181497839586/

https://www.realmoms.com/the-edible-terrarium-has-arrived_/