This goes for all the the games from Dreamnoid that I have played so far.
-The Lightkeeper
-The Trespasser
-Legends of Aereven: Lunar Wake
Note: I have not completed all of Trespasser yet, I only know how to get the Cat Eyes, Bat Wings, and Pistol.
Also, I managed to beat the post game of The Lightkeeper, but unable to find one treasure,