Not 100% if this is a bug or not, but definately stood out to me.
When looking for Temple of Eterra, you go through the time portal, at end of this ancient (I think) portal you face the dragon, you can town portal out sell items and when you return through your portal the dragon is respawned; This can be done infinitly as far as I can tell.
Maybe not something massive, thought I would place it here anyway.
Cheers,
Flowercake!