Dungeons are scattered across the map and come in the form of
caves, ruins, etc. To clear a dungeon, we must defeat all the enemies inside.
When completed, a message will appear on screen. If we've eliminated all visible
enemies and "cleared" hasn't appeared, it likely means there's a hidden passage
somewhere with more enemies. Dungeons that are not cleared will have a "?" above
them.
There are a couple tricky ones, but nothing too hard if we enter at the right
point in time. Once we clear all 52 dungeons, the trophy will unlock.
Here is a checklist of the different dungeons: