I've heard enough context about the island from Lucas and Mathis themselves, and even got a brief glimpse into it from these flickering memories from Izutsumi.

[ Apparently he was there. He liked reading and was religious. Extremely OOC of him. ]

Not enough to get the clearest of pictures, but it doesn't seem like the plot of the ventures in themselves are typically relevant. Sometimes they're related to someone's memory or experiences, other times they're not.