On locking content/areas from players, rewarding explorers.
What's less immediately apparent is the Dark Souls influence. Playing that game was an extremely formative experience for me as a game designer, and has caused me to rethink everything. I've learned some things that aren't supposed to be okay really are okay. For example: Putting a large, stunning, noteworthy portion of the map behind the most unlikely illusionary wall.
http://www.kickstarter.com/projects/1192311215/ghost-song-a-journey-of-hope